Technical Report

TR-10-18

Design, construction and initial stateof the underground openings
Svensk Kärnbränslehantering AB

December 2010

Svensk Kärnbränslehantering AB

Box 250, SE-101 24 Stockholm
Phone +46 8 459 84 00

TR-10-18

CM Gruppen AB, Bromma, 2010

Swedish Nuclear Fueland Waste Management Co

ISSN 1404-0344
Tänd ett lager:
SKB TR-10-18
P, R eller TR.

Design, construction and initial stateof the underground openings
Svensk Kärnbränslehantering AB

December 2010

Keywords: SKBdoc 1177188, Underground openings, Safety report, Designpremise, Observational method, Site adaptation, Verification, Reference design,
Reference methods, Initial state.
A pdf version of this document can be downloaded from www.skb.se.

Preface
An important part of SKB’s licence application for the construction, possession and operation of
the KBS-3 repository is the safety report. The safety report addresses both safety during operationof the KBS-3 repository facility (SR-Operation), and the long-term safety of the KBS-3 repository(SR-Site).
For the construction of the KBS-3 repository SKB has defined a set of production lines:•

the spent nuclear fuel,•the canister,•

the buffer,•

the backfill,•

the closure,•the underground openings.

These production lines are reported in separate Production reports, and in addition there is a Repository
production report presenting the common basis for the reports.
This set of reports addresses design premises, reference design, conformity of the reference design todesign premises, production and the initial state, i.e. the results of the production. Thus the reports provide
input to SR-Site concerning the characteristics of the as built KBS-3 repository and to SR-Operation
concerning the handling of the engineered barriers and construction of underground openings.
The preparation of the set of reports has been lead and coordinated by Lena Morén with support from
Karin Pers, Marie Wiborgh and Roland Johansson.
This report has been authored by Mats Holmberg.

TR-10-18

3

Summary
The report is included in a set of Production reports, presenting how the KBS-3 repository is designed,
produced and inspected. The set of reports is included in the safety report for the KBS-3 repository andrepository facility.
The report provides input on the initial state of the underground openings for the assessment of thelong-term safety, SR-Site. The initial state refers to the properties of the underground openings atfinal disposal, backfilling or closure. In addition, the report provides input to the operational safety
report, SR-Operation, on how the underground openings shall be constructed and inspected.
The report presents the design premises and the methodology applied to design the underground openings and adapt them the to the site conditions so that they conform to the design premises. It presents thereference design at Forsmark and its conformity to the design premises. It also describes the reference
methods to be applied to construct and inspect the different kinds of underground openings. Finally, theinitial state of the underground openings and its conformity to the design premises is presented.
Design premises for the underground openings

The design premises for the underground openings are based on regulations; the functions of the KBS-3
repository; the design basis cases from the assessment of the long-term safety; the design basis eventsfrom the assessment of the operational safety; technical feasibility and the planned construction.
The underground openings shall accommodate the sub-surface part of the KBS-3 repository facility.
The underground openings as such do not contribute to the safety of the KBS-3 repository and do nothave any barrier functions. However, the locations of the deposition holes with respect to the thermal,hydrological and mechanical properties of the rock are important for the utilisation of the rock as a barrier and thus for the safety of the repository. Furthermore, irreversible changes in the rock surrounding
the rock excavation, i.e. the excavation damaged zone (EDZ), and engineered and residual materials thatremain in the rock may impact the barrier functions of the rock and/or the engineered barriers. Designpremises for the acceptable placement of deposition areas and deposition holes as well as restrictions
on engineered and residual materials are provided from the assessment of the long-term safety. The
underground openings shall also be designed to conform to design premises from the engineered barriers
and plugs, and to design premises related the development and operation of the repository facility.
Rock engineering

The objectives of rock engineering are to ensure that the site-adapted layout as well as the construction and as-built underground openings, conform to the design premises. SKB will apply the so called
Observational Method for adapting the layout of the repository and construction of the undergroundopenings to the successively developed description of the site. The design will always be based on
the most recent site descriptive model and consider the most likely ground conditions as well as
possible deviations ranging from most favourable to worst conceivable conditions. Application of
the Observational Method implies that hazards that contribute to the risk for nonconformity to thedesign premises are identified, that models predicting the hazard and calculating parameters that willsubsequently be observed during construction are established, and that action plans for handling of
possible adverse conditions are defined. At designated milestones formal comparisons of the design
assumptions and the encountered ground conditions are performed.
The reference design at Forsmark and its conformity to the design premises

The reference design is the result of the at present completed design step denominated Design step D2.
The site-specific basis for the reference design is geotechnical information compiled in a site engineering
report (SER). The information in the SER builds on the surface-based site investigations carried out at
the Forsmark site and presented in the site descriptive model (SDM). The verification of the conformityof the reference design to the design premises is restricted by the currently anticipated uncertainties
related to the SDM and SER.

TR-10-18

5

The reference design is presented under the subtitles repository depth, deposition areas and deposition
holes, other underground openings and engineered and residual materials. The repository depth isselected to conform to the design premises to find large enough volumes fulfilling the specific requirements on deposition holes and to avoid freezing of buffer and backfill and inadvertent human intrusion.
The deposition areas and placement of the deposition holes shall conform to design premises forfavourable and stable thermal, mechanical and hydrological conditions. The depositions tunnels as wellas other tunnels, ramp and shafts are designed to conform to design premises regarding limitation of the
EDZ. Finally, the amounts of engineered and residual materials in different parts of the undergroundfacilities are estimated and compared to the acceptable amounts.
Reference methods

The reference methods for construction shall result in underground openings in conformity to thedesign premises for EDZ, geometry and inflow. The reference method for excavation of deposition
tunnels is drill and smooth-blasting techniques. Experiences show that provided that proper controlof drilling and blasting procedures are applied tunnels with acceptable EDZ and geometry can beconstructed. The reference method for sealing the deposition tunnels is grouting the rock beyond
the excavation face, i.e. pre-grouting, using low pH cement. Experiences from Äspö Hard RockLaboratory (HRL) show that the inflow limitation imposed by the backfill can be achieved when
detailed design procedures are combined with proper control of the grouting operation.
The reference method for excavating the deposition holes are full-face down-hole drilling techniques.
Experiences from mechanical excavation methods show that it is possible to achieve an EDZ in
conformity to the design premises. Based on experiences from Äspö HRL the geometrical variations
will lie within the acceptable tolerances.
The reference methods also comprise methods for inspection. The method and criterion applied inselecting deposition hole positions will impact the conformity to the design premise to avoid shear
displacements larger than the canister can withstand. The criterion to be applied states that fracturesintersecting the deposition hole and the full perimeter of the tunnel and fractures intersecting fiveor more deposition holes are potentially critical and all affected deposition hole positions shall berejected. It is foreseen that deposition holes having a potential for unacceptable inflows also arelikely to be screened out by this criterion.
Initial state of the underground openings

The initial state of the underground openings refers to the properties of the underground openings atfinal installation of the buffer, backfill, closure or plugs. The presentation of the initial state comprises
a summary of the site adapted design at Forsmark, the properties that can be expected based on theexperiences from the reference methods and an assessment of the risk that the initial state of theunderground openings does not conform to the design premises. In the risk assessment both site conditions, geohazards, and hazards associated with reference methods were considered. The assessment is
at this stage qualitative. Both the likelihood of occurrence for identified hazards and the confidence inthe monitoring and control programmes were considered. The risks were classified as negligible and/or acceptable or significant and/or unacceptable. No significant and/or unacceptable risks were identified. However, the assessment identified several issues of importance for the conformity to the designpremises to be considered in the future development of the design and reference methods.

6TR-10-18

Sammanfattning
Rapporten ingår i en grupp av Produktionsrapporter som redovisar hur KBS-3-förvaret är utformat,
producerat och kontrollerat. Gruppen av rapporter ingår i säkerhetsredovisningen för KBS-3-förvaret
och förvarsanläggningen.
Rapporten redovisar indata om bergutrymmenas initialtillstånd för analysen av långsiktig säkerhet,
SR-Site. Initialtillståndet avser egenskaperna hos bergutrymmena vid slutlig deponering, återfyllning
eller förslutning. Dessutom ger rapporten information till driftsäkerhetsredovisningen, SR-Drift, om
hur bergutrymmena ska byggas och kontrolleras.
Rapporten redovisar konstruktionsförutsättningarna och den metod som tillämpas för att utforma berg­
utrymmena och anpassa dem till förhållandena på platsen så att de överensstämmer med konstruktions­förutsättningarna. Den redovisar referensutformningen i Forsmark och dess överensstämmelse med
konstruktionsförutsättningarna. Den beskriver också referensmetoderna som ska används för att bygga
och kontrollera de olika bergutrymmena. Slutligen redovisas bergutrymmenas initialtillstånd och dessöverensstämmelse med konstruktionsförutsättningarna.
Konstruktionsförutsättningar för bergutrymmena

Konstruktionsförutsättningarna för bergutrymmena är baserade på föreskrifter, KBS-3-förvarets funktioner, konstruktionsstyrande fall från analysen av långsiktig säkerhet, konstruktionsstyrande händelserfrån redovisningen av driftsäkerhet, teknisk genomförbarhet och det planerade uppförandet.
Bergutrymmena ska rymma undermarksdelen av KBS-3-förvarsanläggningen. Bergutrymmena somsådana bidrar inte till KBS-3-förvarets säkerhet och har inga barriärfunktioner. Deponeringshålens
inplacering med hänsyn till bergets termiska, hydrologiska och mekaniska egenskaper är dock viktig
för utnyttjandet av berget som barriär, och således för förvarets säkerhet. Dessutom kan irreversibla
förändringar i berget som omger berguttaget, dvs den skadade zonen (EDZ, excavation damaged zone)
samt konstruktions- och kvarvarande material i berget påverka bergets och de tekniska barriärer­nas barriärfunktioner. Konstruktionsförutsättningar för placering av deponeringsområden och deponerings­hålliksom restriktioner för konstruktions- och kvarlämnat material ges från analysen av den långsiktiga
säkerheten. Bergutrymmena ska också överensstämma med konstruktionsförutsättningar från detekniska barriärerna och pluggarna, och med konstruktionsförutsättningar relaterade till utbyggnad
och drift av förvarsanläggningen.
Bergteknik

Bergteknikens mål är att säkerställa att den platsanpassade layouten samt uppförandet och de byggda
bergutrymmena överensstämmer med konstruktionsförutsättningarna. SKB avser tillämpa den så kallade
observationsmetoden för att anpassa bergutrymmenas layout och utbyggnad till den successivt utvecklade beskrivningen av platsen. Utformningen kommer alltid att baseras på den senaste platsbeskrivande
modellen och överväga de mest troliga bergförhållandena liksom möjliga avvikelser varierande mellan
de mest gynnsamma och de värsta tänkbara förhållandena. Tillämpning av observationsmetoden innebär
att oönskade händelser som bidrar till risken för avvikelser från konstruktionsförutsättningarna identifieras, att modeller som förutsäger dessa händelser och beräknar parametrar som sen ska observeras
under utbyggnaden fastställs, samt att åtgärdsplaner för att hantera tänkbara ogynnsamma förhållanden
identifieras. Vid angivna milstolpar görs formella jämförelser mellan förutsättningarna för utformningenoch de påträffade bergförhållandena.

TR-10-18

7

Referensutformningen i Forsmark och dess överensstämmelse med
konstruktionsförutsättningarna

Referensutformningen är resultatet av det för närvarande avslutade designskedet benämnt Designskede D2.
De platsspecifika utgångspunkterna för referensutformningen är geoteknisk information samman­ställd
i en markteknisk undersökningsrapport (SER, site engineering report). Informationen i SER byggerpå de markbaserade platsundersökningar som genomförts i Forsmark och som presenterats i denplatsbeskrivande modellen (SDM, site descriptive model). Verifieringen av referensutformningens
överensstämmelse med konstruktionsförutsättningarna begränsas av de för närvarande förutsedda
osäkerheterna relaterade till SDM och SER.
Referensutformningen redovisas under rubrikerna förvarsdjup, deponeringsområden och deponerings­
hål, övriga bergutrymmen samt konstruktions- och kvarlämnat material. Förvarsdjupet är valt så
att det överensstämmer med konstruktionsförutsättningar för att påträffa tillräckligt stora områden
som uppfyller kraven på deponeringshål och för att undvika frysning av buffert och återfyllning
samt oavsiktliga mänskliga intrång. Deponeringsområdena och placeringen av deponeringshål skaöverenstämma med konstruktionsförutsättningar för gynnsamma och stabila termiska, mekaniska ochhydrologiska förhållanden. Deponeringstunnlar liksom andra tunnlar, ramp och schakt är utformade så
att de överensstämmer med konstruktionsförutsättningar för begränsning av EDZ. Slutligen beräknas
mängderna konstruktions- och kvarlämnat material och jämförs med acceptabla mängder.
Referensmetoder

Referensmetoderna för utbyggnad ska resultera i bergutrymmen som överensstämmer med
konstruktions­förutsättningarna för EDZ, geometri och inflöde. Referensmetoden för bergschakt
av deponeringstunnlar är skonsam sprängning. Erfarenheter visar att förutsatt att lämplig styrning
av borr- och sprängförfarandet tillämpas så kan tunnlar med godtagbar EDZ och geometri byggas.
Referensmetoden för att täta deponeringstunnlar är injektering framför tunnelfronten, dvs förinjektering, med låg-pH-cement. Erfarenheter från Äspölaboratoriet visar att den begränsning av inflödet
som ges av återfyllningen kan åstadkommas när detaljerade utformningsrutiner kombineras med
lämplig styrning av injekteringsverksamheten.
Referensmetoden för att bygga deponeringshål är nedåtriktad fullborrning. Erfarenheter från mekaniska
bergschaktmetoder visar att det är möjligt att uppnå en EDZ som överensstämmer med konstruktionsförutsättningarna. Baserat på erfarenher från Äspölaboratoriet kommer de geometriska variationerna att
ligga inom de acceptabla toleranserna.
Referensmetoderna omfattar även metoder för kontroll. Metod och kriterium som tillämpas för att
välja deponeringshålens placering påverkar överensstämmelsen med konstruktionsförutsättningen
för att undvika skjuvrörelser större än de kapslarna kan motstå. Det kriterium som ska tillämpas
anger att sprickor som skär deponeringshålet och deponeringstunnelns hela omkrets samt sprickor
som skär fem eller fler deponeringshål är potentiellt riskfyllda och påverkade lägen för deponeringshål ska förkastas. Det förutses att deponeringshål med potential för icke tillåtna inflöden troligtvisockså kommer att sållas bort av detta kriterium.
Bergutrymmenas initialtillstånd

Bergutrymmenas initialtillstånd avser egenskaperna vid slutlig installation av buffert, återfyllning,förslutning eller pluggar. Redovisningen av initialtillståndet omfattar en sammanfattning av denplatsanpassade utformningen i Forsmark, egenskaper som kan förväntas baserat på erfarenheterna av
referensmetoderna samt en analys av risken att bergutrymmenas initialtillstånd avviker från konstruktionsförutsättningarna. I riskanalysen övervägdes både platsförhållanden, oönskade bergförhållanden,och oönskade händelser relaterade till referensmetoderna. Analysen är i detta skede kvalitativ. Bådesannolikheten att de identifierade oönskade händelserna ska inträffa och kontroll- och styrprogrammens tillförlitlighet övervägdes. Riskerna klassificerades som försumbara och/eller acceptabla eller
betydande och/eller oacceptabla. Inga betydande och/eller oacceptabla risker identifierades. Analysen
identifierade dock flera frågor med betydelse för överensstämmelsen med konstruktionsförutsätt­ningarna som ska övervägas i den fortsatta utvecklingen av utformningen och referensmetoderna.

8TR-10-18

Contents
1
1.1

1.2

1.3

1.4
1.5

2
2.1
2.2
2.3

2.4
3
3.1
3.2
3.3
3.4
3.5
4
4.1
4.2

4.3
4.4
4.5

Introduction
General basis
1.1.1 This report
1.1.2 The design of the underground openings
1.1.3 The construction of the underground openings
Purpose, objectives and delimitations
1.2.1 Purpose
1.2.2 Objectives
1.2.3 Limitations
Interfaces to other reports included in the safety report
1.3.1 The safety report for the long-term safety
1.3.2 The safety report for the operational safety
1.3.3 The other production reports
Supporting site descriptive reports and underground openings design reports
1.4.1 Site descriptive reports
1.4.2 Underground design reports
Structure and content
1.5.1 Overview
1.5.2 Design premises
1.5.3 Rock engineering
1.5.4 Reference design and its conformity to the design premises
1.5.5 The methods for construction and inspection
1.5.6 Initial state of the underground openings

11
11
11
11
11
12
12
12
12
13
13
13
13
14
14
14
14
14
15
15
15
15
15

Design premises for the underground openings
General basis
2.1.1 Identification and documentation of design premises
2.1.2 Definitions, purpose and basic design
Required functions and design considerations
2.2.1 Functions of the underground openings in the KBS-3 repository
2.2.2 Design considerations
Design premises
2.3.1 Design premises related to the functions in the KBS-3 repository
2.3.2 Design premises from the engineered barriers and plug
2.3.3 Design premises related to production and operation
Design premises imposed by the underground openings

17
17
17
17
18
18
19
19
20
22
25
26

Rock engineering
GeneralThe Observational Method
3.2.1 Description
3.2.2 Monitoring
Stepwise development of the underground facilities
Control programme
Documentation of as-built/initial-state conditions

27
27
28
28
30
30
31
31

The reference design at Forsmark and its conformity to thedesign premises
Repository depth
Deposition area – placement of deposition holes
4.2.1 Thermal conditions
4.2.2 Mechanical conditions
4.2.3 Hydrogeological conditions
Deposition holes
Deposition tunnels
Other underground openings

33
34
34
34
35
37
37
39
39

TR-10-18

9

4.6

Engineered and residual materials
4.6.1 Rock support in underground openings
4.6.2 Grouting measures in underground openings
4.6.3 Quantities of engineered and residual materials

40
41
41
42

5
5.1
5.2

Reference methods
General basis
Reference methods used for the construction of deposition tunnels
5.2.1 The excavation damaged zone using drill and blast techniques
5.2.2 Geometrical tolerances
5.2.3 Tunnel floor contour
5.2.4 Grouting techniques and grouting results
5.2.5 Recess for the plug in deposition tunnels
5.2.6 Preparation of deposition tunnels
Reference methods used in construction of deposition holes
5.3.1 Excavation damaged zone using mechanical excavation techniques
5.3.2 Geometrical tolerances
5.3.3 Acceptable inflow
5.3.4 Methodology for accepting deposition holes on the basis of adiscriminating fracture
5.3.5 Bevel in the upper part of the deposition hole
5.3.6 Preparation of deposition holes
Reference methods associated with other underground openings

45
45
45
45
46
47
47
48
48
49
49
50
51

Initial state of the underground openings
Introduction
Reference design at the Forsmark site
6.2.1 Repository depth and deposition areas
6.2.2 Deposition tunnels
6.2.3 Deposition holes
Geometry and properties of importance for the initial state of the engineered
barriers
6.3.1 Buffer and deposition holes
6.3.2 Backfill and deposition tunnels
Uncertainty and risk relative to the initial state
6.4.1 General basis
6.4.2 Geohazards, design methodologies and reference methods
6.4.3 Risk matrix
6.4.4 Qualitative risk assessment of the initial state for repository depth
and deposition areas
6.4.5 Qualitative risk assessment of the initial state for deposition tunnels
6.4.6 Qualitative risk assessment of the initial state for deposition holes

55
55
55
55
56
56

5.3

5.4
6
6.1
6.2

6.3

6.4

51
52
52
54

57
57
57
58
58
58
60
61
63
65

References

69

Appendix A Tabulation of data from measurements of as-built volumes in thetunnel excavated by means of smooth-blasting techniques at theÄspö Hard Rock Laboratory

71

Appendix B Tabulation of data from measurements of cross-sectional centre
points and diameters in 6 deposition holes drilled at the Prototype
Repository at the Äspö Hard Rock Laboratory73

10

TR-10-18

1

Introduction

1.1

General basis

1.1.1 This report
This report presents the reference design, construction and initial state of the underground openingsof the KBS-3 repository for spent nuclear fuel. It is included in a set of reports presenting how theKBS-3 repository is designed, produced and inspected. The set of reports is denominated Production
reports. The Production reports and their short names used as references within the set are illustrated
in Figure 1-1. The reports within the set referred to in this report and their full names are presented
in Table 1-1.
This report is part of the safety report for the KBS-3 repository and repository facility, see Repository
production report, Section 1.2. It is based on the results and review of the most recent long-term safetyassessment and on the current knowledge and technology and results from research and development.

1.1.2 The design of the underground openings
The presented design of the underground openings presumes a repository based on the KBS-3 methodwith vertical deposition of canisters in individual deposition holes as further described in Chapter 3 inthe Repository production report.
The reference design and construction methods presented in this report constitute an approach which istechnically feasible. It is, however, foreseen that the design premises, the design as well as the presented methods for construction, test and inspection will be further developed and optimised before
the actual construction of the KBS-3 repository facility commences. This is especially the case forthe underground openings since both the design and the methods of construction require informationon the conditions at repository depth. In this context it should be mentioned that there are alternative
designs that conform to the design premises as well as alternative ways to construct the reference
design. The safety assessment, as well as future safety assessments, may also result in up-dated designpremises. SKB’s objective is to continuously develop and improve both design and production andadapt them to the conditions at the selected site.

1.1.3 The construction of the underground openings
The construction of the underground openings is one of the main activities included in the operation of
the KBS-3 repository facility. The principal layout of the underground openings as well as the sequencein which they are constructed are based on the planned operation of the KBS-3 repository facility
presented in Section 4.1.4 in the Repository production report.
Production reports
Repository
production
reportSpent fuelreport”Engineered barrier” production reports

Canisterproduction
reportBufferproduction
reportBackfill
production
reportClosureproduction
reportUndergroundopenings
construction
reportFigure 1-1. The reports included in the set of reports describing how the KBS-3 repository is designed,
produced, tested and inspected.

TR-10-18

11

Table 1-1. The reports within the set of Production reports referred to in this report.
Full title

Short name used within the
Production line reports

Text in reference lists

Design and production of theKBS-3 repository

Repository production report

Repository production report, SKB 2010.
Design and production of the KBS-3 repository.
SKB TR-10-12, Svensk Kärnbränslehantering AB.

Design, production and initialstate of the buffer

Buffer production report

Buffer production report, SKB 2010. Design,
production and initial state of the buffer. SKB
TR-10-15, Svensk Kärnbränslehantering AB.

Design, production and initialstate of the backfill and plug indeposition tunnels

Backfill production report

Backfill production report, SKB 2010. Design,
production and initial state of the backfill and plugin deposition tunnels. SKB TR-10-16, Svensk
Kärnbränslehantering AB.

Design, production and initialstate of the closure

Closure production report

Closure production report, SKB 2010. Design,
production and initial state of the closure. SKB
TR-10-17, Svensk Kärnbränslehantering AB.

1.2

Purpose, objectives and delimitations

1.2.1 Purpose
The purpose of this report is to describe how the underground openings of the KBS-3 repository
are designed, constructed and inspected in a manner related to their importance for the safety of theKBS-3 repository. The report shall provide the information on the design, construction and initialstate of the underground openings required for the long-term safety report, SR-Site, as well as theinformation on how to construct and inspect the underground openings required for the operationalsafety report, SR-Operation.
With this report SKB intends to present the design premises for the underground openings in theKBS-3 repository and demonstrate how the underground openings can be designed and constructedto conform to the stated design premises. The report shall present the reference design and construction methods and summarise the research and development efforts that supports that the undergroundopenings can be constructed in conformity to the design premises.

1.2.2 Objectives
Based on the above purpose the objectives of this report are to present:
•
•
•
•
•

the design premises for the underground openings,
the reference design of the underground openings,
the conformity of the reference design to the design premises,
the reference methods for construction and inspection,
the initial state of the underground openings, i.e. the expected result of the design and construction comprising as-built data on the properties taken credit for as contributing to, or affecting, thebarrier functions of the rock and safety.

1.2.3 Limitations
This report includes design premises for the underground openings related to nuclear safety and radiation protection and to the dependable construction of the KBS-3 repository . The presented reference
designs of the underground openings must conform to these design premises and consequently they
have in most cases determined the design. Design premises related to other aspects, e.g. environmental impact, workers safety and cost-effectiveness, are only included if they have determined the designof the underground openings or the methods to construct them.

12

TR-10-18

The report presents how the underground openings are constructed to conform to the stated design premises. Other aspects of the construction works, e.g. workers safety or logistics are reported elsewhere.
The report presents the reference design and methods. Alternative designs and planned developmentsof the design and methods are reported elsewhere.
This report also includes the design considerations made with respect to the application of best available
nuclear safety and radiation protection technique. It describes the related design premises for the designand development of methods for construction and inspection of the underground openings. Motivationsof the presented reference design and methods as the best available are reported elsewhere.

1.3

Interfaces to other reports included in the safety report

The role of the Production reports in the safety report is presented in Section 1.2 in the Repository
production report. A summary of the interfaces to other reports included in the safety report isgiven below.

1.3.1 The safety report for the long-term safety
By providing a basic understanding of the repository performance over different time-periods andby the identification of scenarios that can be shown to be especially important from the standpointof risk the long-term safety assessment provides feedback to the design of the engineered barriers
and underground openings. The methodology used for deriving design premises from the long-term
safety assessment is introduced in the Repository production report, Section 2.5.2. A more thorough description as well as the resulting design premises are given in the report “Design premises
for a KBS-3V repository based on results from the safety assessment SR-Can and some subsequent
analyses” /SKB 2009a/, hereinafter referred to as Design premises long-term safety. These designpremises constitute a basic input to the design of the underground openings.
As stated in Section 1.2 this report shall provide information on the initial state of the undergroundopenings and data concerning the design of the underground openings used in the assessment of thelong-term safety.

1.3.2 The safety report for the operational safety
The objectives for the operational safety and radiation protection in the final repository facility
and the general description of the facility and its main activities given in Chapters 3 and 5 of
SR-Operation constitute an input to this report.
This report provides information to SR-Operation on the design of the underground openings andthe technical systems used to construct and inspect them as well as instructions on where and wheninspections shall be performed.

1.3.3 The other production reports
The Repository production report presents the context of the set of Production reports and theirrole within the safety report. It also includes definitions of some central concepts of importance forthe understanding of the Production reports.
The Repository production report sets out the laws and regulations and demands from the nuclear
power plant owners that are applicable to the design of a final repository for spent nuclear fuel. In
addition, it describes the functions of a KBS-3-repository and how the safety is maintained by thebarriers and their barrier functions. The report goes on to describe how design premises are derived
from laws and regulations, owner demands and the iterative processes of design and safety assessment and design and technique development respectively. The starting point for the design premisespresented in this report is the functions and design considerations introduced in the Repository
production report, Chapter 3.

TR-10-18

13

The design and production of the different engineered barriers and underground openings are interrelated. An overview of the design and production interfaces is provided in the Repository production report, Chapter 4. The design premises imposed by the engineered barriers for the undergroundopenings stated in each of the “Engineered barrier” production reports are repeated in this report.
The conformity of the reference designs of the underground openings to these design premises areverified in this report.

1.4

Supporting site descriptive reports and undergroundopenings design reports

1.4.1 Site descriptive reports
SKB has undertaken surface-based site investigations with the purpose to develop a site descriptivemodel (SDM). A SDM is an integrated model for geology, thermal properties, rock mechanics, hydrogeology, hydrogeochemistry, bedrock transport properties and a description of the surface system. The
SDM concluding the surface-based investigations at Forsmark is presented in /SKB 2008a/. It presents
the integrated understanding of the Forsmark site at the completion of the surface-based investigations.
The SDM is comprehensive and serves the needs of many users, to extract data into parameters
required for the design and layout of the underground openings a Site Engineering Report (SER) is
developed. The SER comprise geological constraints and engineering guidelines for design issues
related to the long-term safety of the repository as well as to operational requirements. The SER for
the Forsmark site used in the current design stage, and supporting the design of the undergroundopenings presented in this report, is presented in /SKB 2009c/. It is based on interpretation andevaluation of information in /SKB 2008/.

1.4.2 Underground design reports
SKB has compiled a steering document for the rock engineering works. The steering document
includes the design premises, the design methodology to be applied and instructions for the design
works. Further, it provides an overview of the documents the designers shall use and produce intheir work. The steering document for the current design stage, denominated stage D2, is provided
in  /SKB 2007/.
Design stage D2 has been carried out in accordance to /SKB 2007/. The most significant results
and SKB’s conclusions from the completed design D2 are presented in /SKB 2009b/. The report
describes the proposed underground facility layout, the rock support and grouting in the different
underground openings as well as the construction strategy and stepwise construction of the deposition areas. It also includes an assessment of uncertainty and risk related to the site and facility
layout and design. The report is the main reference to the reference design and initial state of theunderground openings presented in this report.

1.5Structure and content

1.5.1 Overview
The general flow of information in the Underground openings construction report can be
described as follows:
•
•
•
•
•

design premises,rock engineering and design methodology,
the reference design and its conformity to the design premises,
methods for construction and inspection,
initial state.

The listed bullets are further described in the following sections. In addition, the context of the reportis presented in this chapter.
14

TR-10-18

1.5.2 Design premises
The design premises set out the information required for the design. The design premises for theunderground openings are presented in Chapter 2 of this report. The chapter starts with the definitionof the underground openings and their purpose. After that follows a presentation of the functions
the underground openings shall provide to contribute to the safety of the final repository and theconsiderations that shall be made in the design with respect to the application of a well-tried andreliable technique. Finally, the detailed design premises for the underground openings are given.
They state the properties the reference design shall have to maintain the functions and to conform to
the design considerations.
1.5.3 Rock engineering
Chapter 3 outlines the objectives of rock engineering and the methodology to be applied in the design
works. The design methodology providing a framework for the design and construction of the underground openings as well as for adapting their layout to the conditions at the repository site is presented.
1.5.4 Reference design and its conformity to the design premises
In Chapter 4 the reference design of the underground openings is presented. It is based on the currently
completed design stage for the final repository at the Forsmark site. The conformity of the reference
design to each of the design premises presented in Chapter 2 is discussed and concluded on the basis of
the current knowledge of the site.
1.5.5 The methods for construction and inspection
In Chapter 5 the reference methods for construction and inspection of the underground openings arepresented. The presentation includes the current state of development and results from demonstrating
their performance relative to the design premises.
1.5.6 Initial state of the underground openings
In Chapter 6, the initial state of the underground openings and the conformity of the constructed underground openings to the design premises related to the long-term safety of the repository is presented.
The chapter comprises conclusions regarding the layout and its adaptation to the site conditions andthe capability of the reference methods to result in underground openings that conform to the specifications. It also presents an assessment of the risk of nonconformity to the design premises.

TR-10-18

15

2

Design premises for the underground openings

In this chapter the design premises for the underground openings are presented. They comprisethe functions and properties the underground openings shall sustain in the KBS-3 repository andpremises for their design. The required functions and design premises are written in italics.

2.1

General basis

2.1.1 Identification and documentation of design premises
The methodology to derive, review and document design premises is presented in the Repository
production report, Chapter 2. The design premises are based on:
•
•
•
•
•

international treaties, national laws and regulations,the functions of the KBS 3 repository,
the safety assessment,
technical feasibility,
the planned production.

The Repository production report, Section 2.2 includes a presentation of the laws and regulations
applicable for the design of a final repository. Based on the treaties, laws and regulations SKB has
substantiated functions and considerations as a specification of the KBS-3 repository, and as guidelines
for the design of its engineered barriers and underground openings. In Section 3.7.2 of the Repository
production report the functions and properties that the underground openings shall sustain in order
to contribute to the functions of the KBS-3 repository are presented. Section 3.9 of the Repository production report introduces the design considerations to be applied in the design work. The presented
functions of the underground openings and the considerations that shall be applied in the design work
are repeated in Section 2.2 in this report.
The design premises related to the functions of the underground openings in the KBS-3 repository
are based on the results from the latest long-term safety assessment and some subsequent analyses.
These design premises for the underground openings are provided in Design premises long-term
safety, and presented in Section 2.3.1 in this report.
Design premises related to technical feasibility refer to the properties the underground openings shallhave to fit, and work, together with the engineered barriers and other parts of the final repository
during the production. The general approach to substantiate this kind of design premises is presented
in Section 2.5.1 in the Repository production report and the interfaces to the engineered barriers andother parts in the production are summarised in Section 4.9.2 in the Repository production report. In
this report these design premises from the engineered barriers and plugs are presented in Section 2.3.2.
Finally, design premises related to the operation of the KBS 3 repository facility and construction of
the underground openings are presented in Section 2.3.3 in this report. The methodology to substantiate these kinds of design premises is presented in Section 2.5.4 in the Repository production report.

2.1.2 Definitions, purpose and basic design
The underground openings are the cavities constructed in the rock that are required to accommodate
the sub-surface part of the final repository facility. The underground openings comprise:•••

the actual geometry and location of the cavities,
the rock surrounding the openings that is affected by the rock construction works, andengineered materials for sealing and rock reinforcement, and residual materials from performanceof activities in the final repository facility which, at deposition, backfilling or closure, remain in
and on the rock that surrounds the openings.

TR-10-18

17

The underground openings as such do not contribute to the safety of the KBS-3 repository and do nothave any barrier functions. However, the locations of the deposition areas and deposition holes withrespect to the thermal, hydrological, mechanical and chemical properties of the rock are important for
the utilisation of the rock as a barrier and thus for the safety of the repository. Furthermore, disturbances on the rock surrounding the tunnels, i.e. the excavation damaged zone (EDZ), and engineered
and residual materials that remain in the rock may impact the barrier functions of the rock and/or theengineered barriers, and must therefore be known when assessing the safety of the repository.
The underground openings shall accommodate the sub-surface part of the final repository facility.
The principal layout of the KBS-3 repository facility and the nominal dimensions of the undergroundopenings have been decided considering operational requirements, activities in the KBS-3 repository
facility and the dimensions of the engineered barriers and plugs.

2.2

Required functions and design considerations

In this section, the functions and design considerations for the underground openings are presented.
They are based on the functions of the KBS-3 repository presented in Section 3.1.2 in the
Repository production report and have been divided into:•functions and properties that the underground openings shall sustain in order for the final repository
to maintain its safety (Section 2.2.1) and• issues that shall be considered when developing the layout and design of the underground openings
and methods for excavation, grouting, rock reinforcement and inspection (Section 2.2.2).

2.2.1 Functions of the underground openings in the KBS-3 repository
In order for the KBS-3 repository to be able to accommodate all spent nuclear fuel from the currently
approved Swedish nuclear power programme the underground openings shall:•accommodate the sub-surface part of the final repository facility with the number of approved
deposition holes that are required to deposit all canisters with spent nuclear fuel.

In order for the final repository to contain, prevent or retard the dispersion of radioactive substances,
the rock shall provide stable and favourable conditions for the engineered barriers so that their barrier
functions can be sustained for as long as necessary bearing in mind the radiotoxicity of the spent
nuclear fuel. Should the containment provided by the canister be breached, the rock will contribute to
the safety of the final repository by preventing or retarding the dispersion of radioactive substances.
In order for the rock to sustain its barrier functions and to maintain the multi-barrier principle, theunderground openings shall be adapted to the conditions at the repository site so that:••••

thermally favourable conditions are provided and the containment of radioactive substances canbe sustained over a long period of time,mechanically stable conditions are provided and the containment of radioactive substances canbe sustained over a long period of time,
favourable hydrologic and transport conditions are provided and the containment, prevention orretardation of dispersion of radioactive substance can be sustained over a long period of time,
chemically favourable conditions are provided and the containment, prevention or retardation ofdispersion of radioactive substances can be sustained over a long period of time.

In order for the KBS-3 repository to maintain the multi-barrier principle and have several barriers
which individually and together contribute towards maintaining the barrier functions, the undergroundopenings shall:•be designed so that they do not significantly impair the barrier functions of the rock or theengineered barriers.

In the design of the KBS-3 repository unintentional intrusion shall be considered so that the repository site after closure of the repository facility can be utilised without compromising the freedom

18

TR-10-18

of action, needs and aspirations of future generations. With respect to this and the fact that the final
repository shall isolate the spent fuel from the environment at the surface:•

the repository depth shall be selected with respect to the human activities which, based on present
living habits and technical prerequisites, may occur at the repository site.

In order for the barrier system of the final repository to withstand failures and conditions, events andprocesses that may impact their functions, the underground openings shall:••allow the deposition of canister and buffer with the desired barrier functions,allow the installation of backfill and closure with the desired barrier functions.

The latter is also required in order for the barriers of the closed final repository to be passive, and inorder for it to be technically feasible to close and seal the final repository facility after the deposition
has been carried out.
For the nuclear operation of the final repository facility to be safe, the underground openings shall:•be designed so that breakdowns and mishaps in connection with the nuclear operations
are prevented.

The underground openings shall also be designed so that other activities in the final repository facility
can be carried out in a safe way.

2.2.2 Design considerations
In this section the design considerations that shall be regarded in the design of underground openings
and the development of construction methods as well as the methods for monitoring and inspectionsof the underground openings are presented.
The system of barriers and barrier functions of the final repository shall withstand failures and conditions, events and processes that may impact their functions. Hence the following shall be considered.
•

Excavation, sealing and rock reinforcement shall be based on well-tried or tested technique.

The construction and inspections of the underground openings shall be dependable, and the following
shall be considered.
••

The underground openings shall be designed and constructed using methods so that they, withreliability, acquire the specified properties.
The properties of the underground openings shall be possible to inspect against specified criteria.

Further, environmental impact such as noise and vibrations, emissions to air and water, impact
on groundwater and consumption of material and energy shall also be considered in the design.
Methods to construct and inspect the underground openings must also conform to regulations foroccupational safety. Requirements related to these aspects can generally be met in a number ofalternative ways for designs that conform to the safety and radiation protection requirements.

2.3

Design premises

In this section the design premises for the underground openings are given. The design premises constitute a specification for the design of the underground openings. The design premises comprise theproperties to be designed and premises for the design such as quantitative information on features,
performance, events, loads, stresses, combinations of loads and stresses and other information, e.g.
regarding environment or adjacent systems, which form a necessary basis for the design.
The design premises are based on the functions the underground openings shall have in the final
repository presented in Section 2.2.1 and the design considerations presented in Section 2.2.2. They
are also based on, and constitute a concise summary of, the current results of the design processwith its design–safety assessment and design–technical feasibility iterations, see Section 2.5.1 in the
Repository production report.

TR-10-18

19

The design premises given as feedback from the long-term safety assessment are compiled in Designpremises long-term safety.
The design premises given as feedback from the technical development are based on the reference
designs of the other parts of the KBS-3 repository and the plans for the main activities and operationof the KBS-3 repository facility presented in Section 4.1.4 in the Repository production report.

2.3.1 Design premises related to the functions in the KBS-3 repository
The design premises for the underground openings related to their functions in the KBS-3 repository
are compiled in Table 2-1 (A-C). In the left hand column of the table the functions which form thebasis for the design premises and that were presented in Section 2.2.1 are repeated, the middle column
contains the underground opening property to be designed and adapted to the site and the right handcolumn gives the design premises as stated in Design premises long-term safety.
Table 2-1. The functions, the related properties and parameters to be designed and the designpremises for the underground openings.
A. Repository depth and deposition areas
Function

Property to be designed

Design premises long-term safety

The underground openings shallaccommodate the sub-surface partof the final repository facility with
the number of approved deposition
holes that are required to deposit all
canisters with spent nuclear fuel.

Deposition areas – utilised rockdomains, distances between deposition holes and loss of deposition holepositions.
Repository depth

The repository volumes and depth
need to be selected where it ispossible to find large volumes of rockfulfilling the specific requirements on
deposition holes.
The requirements on deposition holes
include acceptable thermal, mechanical, hydrological and transportconditions.
The repository shall have sufficient
capacity to store 6,000 canisters.1

The underground openings shall be
adapted to the rock so that thermallyfavourable conditions are provided
and the containment of radioactive
substances can be sustained over along period of time.

Repository depthWith respect to potential freezing of
buffer and backfill, surface erosion
and inadvertent human intrusion,
the depth should be considerable.
Analyses in the SR-Can assessments
corroborate that this is achieved byprescribing the minimum depth to be
as specified for a KBS-3 repository,
i.e. at least 400 m.

Deposition areas – utilised rockdomains, hydrogeochemical conditions.
Repository depth

Reducing conditions;
Salinity; TDS limited
Ionic strength; [M2+] > 1 mM
Concentrations of K, HS−, Fe; limited
pH; pH < 11
Avoid chloride corrosion; pH > 4 or[Cl−] < 3 M.

The repository depth shall be selectedwith respect to the human activities
which, based on present living habits
and technical prerequisites, may
occur at the repository site.
The underground openings shall be
adapted to the rock so that chemicallyfavourable conditions are provided
and containment, prevention orretardation of dispersion of radioactive
substances can be sustained over along period of time.

1
This is not a design premise from the long-term safety. It is an estimation based on the number of spent fuel assemblies to be encapsuleted and deposited.

B. Deposition holes
Function

Property to be designed

The underground openings shall be
adapted to the rock so that thermallyfavourable conditions are provided
and the containment of radioactive
substances can be sustained overa long period of time.

Deposition holes – distances between The buffer geometry (e.g. void
deposition holes.
spaces), water content and distances
between deposition holes should beselected such that the temperature in
the buffer is <100°C.

20

Design premises long-term safety

TR-10-18

Function

Property to be designed

The underground openings shall be
adapted to the rock so that mechanically stable conditions are provided
and the containment of radioactive
substances can be sustained overa long period of time.

Deposition holes – respect distance to Deposition holes are not allowed to be
deformation zone.
placed closer than 100 m to deformation zones with a trace length longer
than 3 km.
Deposition holes – intersecting
fractures (mechanical properties).

The underground openings shall be
Deposition holes – inflow
adapted to the rock so that favourablehydrologic and transport conditions
are provided and the containment,
prevention or retardation of dispersionof radioactive substances can besustained over a long period of time.

Design premises long-term safety

Deposition holes should, as far as
reasonably possible, be selected
such that they do not have potential
for shear larger than the canister canwithstand. To achieve this, the EFPC1
criterion should be applied in selecting
deposition hole positions.
The total volume of water flowing
into a deposition hole, for the time
between when the buffer is exposed
to inflowing water and saturation,
should be limited to ensure thatno more than 100 kg of the initiallydeposited buffer material is lost due topiping/erosion. This implies, according
to present knowledge, that this total
volume of water flowing into an
accepted deposition hole must be lessthan 150 m3.

Deposition holes – intersecting
Fractures intersecting the deposition
fractures (hydrogeological properties). holes should have a sufficiently low
connected transmissivity (specificvalue cannot be given at this point).
This criterion is assumed to be fulfilled
if the conditions regarding inflow todeposition holes are fulfilled.
The underground openings shall be
designed so that they do not significantly impair the barrier functions of
the rock or the engineered barriers.

1

Deposition holes – transmissivity of
EDZ.

Before canister emplacement, theconnected effective transmissivity
integrated along the full length of thedeposition hole wall and as averaged
around the hole, must be less than
10–10 m2/s.

EFPC stands for Extended Full Perimeter Intersection Criterion, see Section 4.2.2 and Figure 4-2.

C. Deposition tunnels, other underground openings and engineered and residual materials
Function

Property to be designed

Design premises long-term safety

The undergroundopenings shallbe designed sothat they do notsignificantly impair
the barrier functions of the rockor the engineered
barriers.

Deposition tunnels– transmissivity of EDZ.

Excavation-induced damage should be limited and not
result in a connected effective transmissivity, along asignificant part (i.e. at least 20–30 m) of the disposal
tunnel and averaged across the tunnel floor, higher
than 10-8 m2/s. Due to the preliminary nature of thiscriterion, its adequacy needs to be verified in SR-Site.

Shafts and ramp, rock caverns and tunnels other than deposition tunnels– transmissivity of EDZ.

Below the location of the top sealing, the integrated
effective connected hydraulic conductivity of thebackfill in tunnels, ramp and shafts and the EDZ
surrounding them must be less than 10-8 m/s. Thisvalue need not be upheld in sections where e.g. thetunnel or ramp passes highly transmissive zones.
There is no restriction on the hydraulic conductivity inthe central area.

Grouting and rock reinforcement in deposition tunnels – extent/design, leachingproduct of grouting material.

Only low pH materials (pH<11)
No continuous shotcreteContinuous grouting boreholes outside tunnel­perimeter should be avoided.

Grouting and rock reinforecement inboreholes shafts and ramp, rock caverns
and tunnels other than deposition tunnels– leaching product of grouting material.

Only low pH (<11) materials are allowed below thelevel of the top seal.

Engineered and residual materials in allunderground openings – amounts andcomposition.

Other residual materials must be limited – but theamounts considered in SR-Can are of no consequence.

TR-10-18

21

2.3.2 Design premises from the engineered barriers and plug
In this section the design premises for the underground openings imposed by the engineered barriers
and plugs related to technical feasibility are presented. Note that interdependencies between theunderground openings and other parts of the final repository occurring after the initial state areconsidered in the design premises related to the functions of the underground openings in the final
repository, presented in Table 2-1.
Buffer

A background to the design premises imposed for the deposition holes by the buffer is given in the
Buffer production report, Section 2.4.1. The deposition hole shall allow dependable installation of
the buffer according to specification. To achieve this, the design premises presented in Table 2-2 andillustrated in Figure 2-1 are imposed by the buffer for the deposition holes.
The stated deviations in radii include all possible causes, e.g. alignment, straightness, displacements
and rock fall out. The stack of bentonite blocks is positioned so that the centre line of the blocks
coincides with the average vertical centre line of the deposition hole.
Backfill

A background to the design premises imposed for the deposition tunnels by the backfill is given in the
Backfill production report, Section 2.4.1. The deposition tunnels shall allow dependable installationof the backfill according to specification. To achieve this, the design premises presented in Table 2-3 are
imposed by the backfill for the deposition tunnels.
Plug in deposition tunnels

A background to the design premises imposed for the deposition tunnels by the plug is given in the
Backfill production report, Section 2.6.1. The deposition tunnels shall allow dependable installation of the plug in deposition tunnels according to specification. To achieve this, the design premisespresented in Table 2-4 are imposed by the plug for the deposition tunnels. The deposition tunnels
shall conform to these design premises during the operational phase of the final repository facility.
Table 2-2. Design premises imposed by the buffer for the deposition holes.
Required property

Design premises

The diameter and height of the deposition
hole shall allow sufficient room to accommodate the buffer and canister.

Nominal thickness of the buffer around, below and above the canister(0.35 m; 0.5 m and 1.5 m).
Nominal dimensions of the canister, Canister production report,
Section 3.2.3.
Resulting diameter 1.75 m
Resulting height 6.68 m

The deposition hole bottom inclination shallwith respect to the dimensions of the buffer
blocks allow deposition of the canister.

The inclination over the part of the cross section where the bottom buffer
block is placed shall be less than 1/1,750.

Variations in deposition hole geometry mustnot be larger than to allow deposition of
buffer according to specification.

In that part of the deposition hole where buffer is going to be installed
the maximum area in each horizontal cross section must not exceed thenominal cross section by more than 7%.
In that part of the deposition hole where buffer is going to be installed
the diameter shall be at least 1.745 m. The nominal diameter is 1.75 m.
From the height of the buffer block on top of the canister to the bottomof the deposition hole the radius from a vertical line in the centre of thedeposition hole shall be at least 0.84 m.
From the height of the buffer block on top of the canister to the bottomof the deposition hole the radius from a vertical line in the centre of thedeposition hole must not exceed 0.925 m.

22

TR-10-18

Nominal tunnel floor

1.75 mrmax= 0.925 m

rmin= 0.84 m-5 mm
Max 7 % of
nominal volume
Bottom inclination
max 1/1,750

6.68 m
6.68 m + bottom plate thickness

rmin= 0.84 mA

rmax= 0.925 m
A

A-A
All cross sections,from the height/depthof the block on top of the canister and downalong the hole, projected in the horizontal
plane shall lie within the blue circle.

rmax= 0.925 m
rmin= 0.84 m
Minimum diameter (redline)
Maximum andMaximum rock fall out (darkgrey)
minimum radii

Figure 2-1. Nominal deposition hole geometry (black thin line) and acceptable deviations in geometry(red dotted line). The scale of the deviations in section A-A is enlarged with a factor of two. The acceptabledeviations concern the part of the deposition hole where the buffer is going to be installed. The top of thedeposition hole is designed with respect to operational requirements.
Table 2-3. Design premises imposed by the backfill for the deposition tunnels.
Required property

Design premises

The deviations of floor and wall surfaces in deposition
tunnels from the nominal must be limited in order to allow
backfilling according to specification.

For each blast round the total volume between the rockwall contour and the nominal contour of the deposition tunnel shall be less than 30% of the nominal tunnel volume.
The maximum cross section shall be less than 35% larger
than the nominal cross section.
To achieve a dependable backfill installation the tunnel
floor must be even enough for the backfill installationequipment to drive on it.
Underbreak is not accepted.
See Figure 2-2

The floor and wall surfaces in deposition tunnels shall forthe most part consist of rock surface so that the backfill
will be in direct contact with the rock.

Limited areas may be covered with construction materials.
The areas must not extend over the full tunnel width.

The seepage into deposition tunnels during backfill
Based on current experiences the maximum distributed
installation and saturation must not significantly impair the inflow to the deposition tunnel is set to be less then or
backfill barrier functions.
equal to 1.7 l/min 100 m (based on 5 l/min in a 300 mlong deposition tunnel) and the maximum point inflow lessthan or equal to 0.1 l/min.

TR-10-18

23

A

A

4.8 m

LBlasting round

Nominal tunnel volume Anominalx∆ L m3
Determined by activities, technical systems and equipmemt

4.2 m

A-A
Accepted volume exceeding the nominal: 0.30xAnominalxLBlasting round m3
2
Accepted largest cross section exceeding the nominal: 0.35xAnominal m
Accepted tunnel floor irregularities: Adapted to backfill installationequipment

Figure 2-2. Nominal tunnel geometry and acceptable volume of rock fall out and irregularities in thetunnel walls.
Table 2-4. Design premises imposed by the plug for the deposition tunnels.
Required property

Design premises

Inflow/seepage of water to the part of the deposition tunnel where The accepted inflow is not determined at this stage
the plug shall be installed must be limited since excessive waterof development.
inflow during construction of the concrete plug may impact theproperties of the finished plug.
A recess for foundation of the concrete plug shall be prepared in Geometry of the reference concrete plug.
the rock.
Geometry and loads according to the reference
Anchoring for structures for the installation of the plug shall be
design of the plug.
prepared in the rock.
The strength and properties of the rock in the area of the location The forces transmitted from the plug to the rock.
of the plug shall be suitable for construction of the recess for theconcrete plug and anchoring of temporary structures.

ClosureThe reference design of the closure is presented in the Closure production report, Sections 3.1 to3.4. In the reference design the main and transport tunnels and ramp and shafts below the top seal,i.e. below the elevation of –200 m, are filled with clay. The remaining cavities, i.e. caverns in thecentral area and ramp and shaft above the elevation of –200 m, are filled with rock fill. The reference
design for clay closure is a block-concept similar to the backfill in deposition tunnels but with higher
acceptable hydraulic conductivity. Accordingly, the closure of these parts of the repository imposes
similar design premises for the underground opening in question, as the backfill does for the deposition tunnels. However, the acceptable variations will deviate from those imposed by the backfill on
deposition tunnels. The acceptable variations in tunnel and shaft volumes will be determined before
excavating these volumes, in parallel to the development of the closure design. Most probably larger
deviations than in the deposition tunnels can be accepted. At this stage of development the properties
to be designed and qualitative design premises are given in Table 2-5.
In addition, to limit the probability that closed investigation boreholes will form water conductive
channels that may jeopardise the barrier functions of the rock the locations of the boreholes haveto be considered in the layout of the final repository facility. It must be avoided that boreholes
connected to the surface intersect underground openings. Further, deposition holes must not beintersected by any investigation boreholes.

24

TR-10-18

Outer edgeof the plug

1.66
2.

11

1.
96

1.50

Inner edgeof the plug

1.21

°

52

Theoretical inneredge of the plug

4.20

3.16

R5.5

0

1.70

Tunnel section
considering
offset of 0.3 m

1.50

0.30

Theoreticaltunnel section

4.80
6.32
9.32

0.3 m offset
assumedFigure 2-3. Nominal geometry for the plug.
Table 2-5. Design premises imposed by the closure in underground openings that will bebackfilled with clay.
Required property

Design premises

The floor and wall surfaces of underground openings
where the closure consist of clay material must be evenenough to allow backfilling according to specification.

Restrictions on volume between the rock wall contour andthe nominal contour.
Underbreak is not allowed.

The seepage into the underground openings during instal- Acceptable inflow preliminary set to the levels stated inlation and saturation of the closure must not significantly
Section 2.3.3.
impair the closure barrier functions.
For a backfilled underground opening to maintain its function, the floor and wall surfaces of the underground opening
shall for the most part consist of rock surface so that theclosure material will be in direct contact with the rock.

Currently, no design premise has been set for thisproperty. However, roads and other structures installed tofacilitate the operation must be removed before the startof closure activities.

Plugs in underground openings other than deposition tunnels

There will be plugs also in tunnels other than deposition tunnels, ramp and shafts. The purposes ofthese plugs can be to separate filled and closed underground openings from underground openings
that remain to close, to cut of conductive features in the rock or to facilitate the installation of theclosure, see the Closure production report, Section 3.6. It is anticipated that these plugs will impose
similar design premises for the underground openings as the plugs in deposition tunnels. The designpremises will be determined in parallel to the detailed design of the plugs.

2.3.3 Design premises related to production and operation
In this section the design premises for the underground openings related to their construction andthe operation of the KBS-3 repository facility are given. In addition to the functions and design
considerations presented in Section 2.2, they are based on how the main activities in the repository
facility are planned to be carried out and on SKB’s objective to minimize radiation doses during theoperation of the KBS-3 repository facility presented in SR-Operation, Chapters 1, 3 and 5.
The layout of the underground openings, the grouting and rock reinforcement shall be designed
so that breakdowns and mishaps in connection to the nuclear operation are prevented. Further, thedesign of the underground openings shall allow activities in the repository facility to be carried out
in a safe and cost-effective way with acceptable impact on the environment and on groundwaterlevels. With respect to this the maximum allowed inflow to shafts, rock caverns and tunnels otherthan deposition tunnels is preliminary set to Q ≤ 10 litre/min 100 m. Design premises related tonuclear operations are given in Table 2-6.

TR-10-18

25

Table 2-6. Design premises for the underground openings related to the nuclear operation of the
final repository facility.
Design consideration or function

Required property

The underground openings shallbe designed so that breakdowns
and mishaps in connection with thenuclear operations are prevented.
The underground openings shall allow
the deposition of canister and installation of buffer with desired barrier
functions.

The placement of the deposition hole Deposition tunnel geometry.
within the deposition tunnel crossInstallation equipment for buffer.
section shall allow deposition of buffer
Deposition machine.
and canister.

The underground openings shallbe designed so that breakdowns
and mishaps in connection with thenuclear operations are prevented.

Underground opening stability, rockreinforcement in underground openings where the canister is handled– extent/design

2.4

Design premises

The frequency of the event: “Rockfalling on the canister and damaging
it so it is no longer fit for deposition.”must not exceed 10–3.

Design premises imposed by the underground openings

The underground openings do not impose any design premises for the engineered barriers or otherparts in the final repository.
The construction of the underground openings may, due to the occurrence of vibrations, impose that
there shall be a respect distance between construction works and completed parts of the final repository, i.e. deposition holes where installation of the buffer and deposition of the canister is completed
and backfilled deposition tunnels.

26

TR-10-18

3

Rock engineering

3.1

GeneralThe design premises for the underground openings were presented in Chapter 2. The objectives ofrock engineering are to ensure that the site-adapted layout of the repository facility, as well as theconstruction and as-built underground openings, conform to those design premises.
Engineering projects are divided into design and construction. The design is carried out successively
as more detailed conditions for the site becomes available. The current reference design – D2 /SKB
2009b/ – documents the preliminary design for the underground part of the repository facility basedon the site conditions given in SDM-Site /SKB 2008/. The design preceding the construction, i.e.
the detailed design, will deliver the specifications and engineering drawings for the layout andunderground openings that will form the Final repository.
In all phases of underground design and construction, uncertainties with regard to site conditions
must be anticipated. In order to establish a final layout for deposition tunnels and deposition holes,
a large volume of rock will have to be characterised, see Figure 3-1. The uncertainties that will
influence the final layout are the spatial location and variability of the geological setting and the rockmass response to excavation, rock support and grouting measures. These uncertainties and the scaleof the repository volume emphasize that the methodology used to adapt the final layout of the repository to the site conditions must be integrated with the construction activities required to develop therepository. The methodology that SKB will use for adapting the layout of the repository to the site
conditions is based on the Observational Method /Peck 1969/.

Operation area
Rock heap

Ventilation

Ramp

Shaft

Ventilation

Repository area

Central area

Figure 3-1. Illustration of the layout contained in the D2 Reference Design for a final repository facility
in Forsmark.

TR-10-18

27

3.2

The Observational Method

The Observational Method is a risk-based approach to underground design and construction that
employs adaptive management, including monitoring and measurement techniques /SKB 2009b/.
The Observational Method was developed for large scale projects where the complexity and spatial
variability of the geological setting prohibits knowing the detailed site conditions prior to construction. Consequently the Observational Method must provide for the collection of site information in
conjunction with construction.

3.2.1 Description
The formal requirements of the Observational Method are found in the European standard for construction and geotechnical design, Eurocode 7 /EN 1997-1:2004, Section 2.7/. The main elements of the
Observational Method are:
1. acceptable limits of behaviour shall be established,
2. the range of possible behaviour shall be assessed and it shall be shown that there is anacceptable probability that the actual behaviour will be within the acceptable limits,
3. a plan for monitoring the behaviour shall be devised, which will reveal whether the actual
behaviour lies within the acceptable limits,
4. the response time of the monitoring and the procedures for analysing the results shall be
sufficiently rapid in relation to the possible evolution of the system,
5. a plan of contingency actions shall be devised which may be adopted if the monitoring reveals
behaviour outside acceptable limits.
SKB will apply the Observational Method for adaptation of the repository to the site conditions, sothat the as-built layout and underground openings conform to the design premises. Application of the
Observational Method requires the following.
(1) One must be able to define an action plan for possible adverse conditions. This implies that themethod cannot be used if a predictive model for the behaviour cannot be developed, i.e.
one must be able to establish a model that can calculate the parameters that will subsequently beobserved during construction.
(2) One must be able to monitor the parameters that can predict behaviour. This is not a trivial
problem as often we can measure what we cannot calculate and vice versa. This means that themonitoring plan must be chosen very carefully with a good understanding of the significance tothe problem. Erroneous preconceptions about the dominant phenomena that control the behaviour
can lead to choosing irrelevant observational parameters.

The detailed design will be based on the SDM and consider the most likely ground conditions as wellas possible deviations ranging from most favourable to worst conceivable conditions. The applicationof the Observational Method is based on identification of hazards, i.e. uncertainties that may contributeto the risk for nonconformity of the layout and underground openings to the design premises. The
preliminary design D2 identified the uncertainties in the site geological conditions, termed geohazards,
that could impact the design and repository layout. The impact of these geohazards was assessed in
the preliminary design using qualitative risk assessment methodologies. A similar procedure will be
adopted during the detailed design.
The Observational Method is a formal design procedure requiring a formal comparison, at designatedmilestones, of the design assumptions and encountered ground conditions. The comparisons shallassess if the layout used to accommodate the site conditions satisfies the design premises. If deviations from the design should occur a formal review by the Safety in Project (SIP) team is required.
This implies that parameters used to monitor the conformance of the layout to the design premisesmust be clearly identified and acceptance criteria (threshold levels) quantified beforehand. SKB’s
application of the Observational Method is illustrated in Figure 3-2.

28

TR-10-18

Design Premises
REFERENCE DESIGN
Site Model & Reference Layout
Functional Requirements
Geohazards/Uncertainties
CONSTRUCTION/OPERATIONSOM Activities
Documentation/Mapping
Monitoring/Inspections
Site model confirmation

Model
Prediction

As-Built
Model

Model
Comparison

No

CRITERIA
MET

ModelComparison
Criteria

Safety In Project
Assess impact
Mitigative
ActionNo
ImpactYesContinue
Construction&
Operations

As-built Report
Initial state

Figure 3-2. Illustration of SKB’s implementation of the Observational Method for repository design.

TR-10-18

29

3.2.2 Monitoring
The monitoring activities required for implementing the Observational Method are dependent on therepository functional requirements and the particular geohazard being monitored. The details of themonitoring programme will be developed successively. For example /SKB 2009b/ identified the frequency of water bearing fractures and the associated inflows in fracture domain FFM02 as the geohazard with the greatest consequence for the repository access. Therefore the groundwater inflows to
the access ramp and the associated drawdown of the groundwater head around the excavation requiremonitoring. In addition, to verifying the SDM, an assessment of the fracture orientations on which
the inflows are occurring and their spatial distribution is also required. The groundwater conditions
encountered will be documented using formal as-built reporting guidelines. The as-built conditions
will be compared to the predictions made prior to the beginning of construction. The comparison
must be carried out using criteria developed during the detailed design preceding the construction
and will take place once the repository access reaches a particular milestone or checkpoint. If thecomparison shows that the actual site conditions deviates outside the predicted variability, and thatthe consequence of such deviation is significant, the as-built conditions are reported to the SIP for
review and possible mitigating measures, see Figure 3-2. Clearly the criteria for comparing the asbuilt conditions with the predicted conditions must be developed in detail and fully specified. In thisexample such criteria can only be specified once the expected ground conditions for the repository
access excavations have been established. Hence investigations will be required before hand toestablish the ground conditions in sufficient detail to establish the criteria.
In the given example the geohazard, i.e. groundwater inflow, can be predicted and it can be measured
directly. However, in other situations the geohazard cannot be measured directly. For example, whilein situ stress is recognized as a geohazard, the maximum horizontal stress is measured indirectly
using either hydraulic fracturing, overcoring or convergence methods. In this example the criteria
for comparing the as-built conditions encountered with the predictions, must also specify themethodology used to interpret the indirect measurement. Regardless of the measuring and monitoring requirements, procedures and guidelines must be developed with the understanding that a main
purpose of the investigations and monitoring is to assess site conditions that were used as the basis
for the detailed design and to quantify the deviations from those conditions should they occur.

3.3

Stepwise development of the underground facilities

The development of the underground facilities is carried out in stages. Initially the accesses to repository depth are developed, followed by the central area and the deposition tunnels and holes for the test
operation. Finally, during the routine operation, the repository will be developed in stages. During eachstage deposition works and rock construction works are carried out in parallel on opposite sides of apartition wall, see Repository production report, Section 4.1.4. Each stage comprises the constructionof deposition tunnels and holes required for a given number of canisters. During each development
stage deposition works are carried out in the part of the deposition area completed in the previous stage,
and detailed site investigations are performed for the deposition tunnels and holes to be constructedin the next stage. Thus there are three separate activities associated with a stage in the development ofdeposition areas:
1. investigation of the detailed site conditions and the adapting of the layout to those conditions,
2. construction of deposition tunnels and deposition holes, and3. deposition works including deposition of canisters and installation of buffer, backfill and plug at
the end of deposition tunnels.
The step-wise development of the deposition areas will enable systematic auditing of the design andconstruction activities.

30

TR-10-18

3.4

Control programme

The control programme shall ensure, using standard quality control and assurance procedures, thatthe construction works and constructions methods conform to the reference methods. The main
objective of the control programme is to secure that the reference methods perform in such a waythat the design premises, quality and efficiency are fulfilled.
With respect to long-term safety the control programme embraces, but is not limited to:•••inspection of delivered material in terms of quantity and quality,
control and inspection of construction works e.g. grouting and excavation activities,
inspection of the results of the construction works e.g. inflow, geometry and excavation damage zone.

The control programme and its quality documentation constitute the basis for the evaluation if theperformance of the reference methods has been acceptable with respect to long-term safety. The
quality documentation comprises, but not limited to:•••

documentation of the performance of material and reference methods,
documentation of quality related to the design premises, and any non-conformity and related
correcting measures,as-built drawings containing positions and geometry and material.

The overall requirements and objectives of the control programme will be defined before the start ofthe construction. Experiences will be obtained successively during the excavation of the repository,
which may result in modification to the reference methods in order to meet the design premises.

3.5

Documentation of as-built/initial-state conditions

As illustrated in Figure 3-2 the formal documentation of the in situ conditions and the layout adopted
for those conditions are provided in an as-built documentation. The formal requirements for the content
of the as-built documentation will be developed in conjunction with the requirements for the test
operation. The documentation will provide information for the initial state of the deposition tunnels andholes completed during a development stage and include the following tentative contents.
1. The spatial location of the boundaries of the deposition area.
2. The spatial location of investigation boreholes.
3. The spatial location of the deposition tunnels.
4. The spatial location of the accepted and rejected deposition holes.
5. Documentation of inspections and inspection-results that demonstrate conformity to thedesign premises.
6. Documentation of any non-conformity related to long-term safety and related mitigative measures.
7. Documentation of all engineered materials left in the rock mass.
In parallel to the development of the main tunnels, deposition tunnels and holes the rock mass conditions are documented as part of the development of the SDM for the deposition area.

TR-10-18

31

4

The reference design at Forsmark and its
conformity to the design premisesThis chapter presents the reference design of the underground part of the KBS-3 repository facility
located in Forsmark and the conformity of the underground openings to the design premises statedin Section 2.3. The reference design is the result of the completed Design step D2. The results from
Design step D2 have been reported in several individual design reports. The most significant results
and SKB’s conclusions from Design step D2 are presented in /SKB 2009b/, which is the main reference for this chapter.
The reference design reflects the current level of detail and the current status of rock engineering
for the underground facilities at Forsmark. The underlying design methodology and the engineeringtasks that have been undertaken to establish the reference design in Design step D2 are described in/SKB 2007/. The conceptual layout and nominal dimensions of the underground openings are given
in /SKB 2007/. Additional design premises for the dimensions of the underground openings imposedby the engineered barriers and plug are presented in Section 2.3.2.
The reference design represents one possible layout of the underground facilities at Forsmark. It
also comprises an estimation of material quantities for rock support and grouting. The site-specificbasis for the reference design is geotechnical information, which has been interpreted and evaluatedin a SER (site engineering report) /SKB 2009c/. The information presented in /SKB 2009c/ builds
on the extensive surface-based site investigations carried out at the Forsmark site and presented in
the SDM (site descriptive model) /SKB 2008/. It is important to point out that the verification of theconformity of the reference design to the design premises stated in Section 2.3 is restricted by thecurrently anticipated uncertainties related to the SDM and SER. The reference design established in
Design step D2 will be the basis for the next design step. The successive excavation of undergroundopenings will provide information that reduces uncertainties with regard to the SDM and SER, andthe reference design will gradually be developed in accordance with the overall design methodology
presented in Chapter 3.
In Section 2.3 the design premises for the underground openings are divided into design premises:•••

related to the functions in the KBS-3 repository,
from the engineered barriers and plug,
related to the production and operation.

In the following sections the reference design and its conformity to these design premises arepresented. The design premises related to the functions in the final repository are presented under thesubtitles:
•
•
•
•
•
•

repository depth,
deposition areas,
deposition holes,
deposition tunnels,
other underground openings,
engineered and residual materials.

Issues related to design premises from engineered barriers and production and operation are also
included in the above subtitles.
The EDZ (excavation damaged zone), dimensions and tolerances of underground openings as well as
grouting, are further discussed in Chapter 5 Reference methods.

TR-10-18

33

4.1

Repository depth

The following design premises are stated for the repository depth and deposition areas in Designpremises long-term safety.
•

The repository volumes and depth need to be selected where it is possible to find large volumesof rock fulfilling the specific requirements on deposition holes.

•

With respect to potential freezing of buffer and backfill, surface erosion and inadvertent human
intrusion, the depth should be considerable. Analyses in the SR-Can assessments corroboratethat this is achieved by prescribing the minimum depth to be as specified for a KBS-3 repository,
i.e. at least 400 m.

•

With respect to hydrogeochemical conditions the following is stated:o reducing conditions; salinity – TDS limited; ionic strength – [M2+] > 1 mM; concentrationsof K, HS−, Fe – limited; pH – pH < 11; avoid chloride corrosion – pH > 4 or [Cl−] < 3 M.

The reference depth was established considering these design premises and the constructabilityof the deposition tunnels and deposition holes. The main influence of the design premises statedin Design premises long-term safety on the reference depth is the hydrogeology of the site, i.e.
frequency and occurrence of transmissive fractures and its correlation to depth, while the influence
on depth from constructability is mainly related to rock mechanical issues, e.g. the likelihood andextent of spalling in deposition holes prior to emplacement.
A rationale for identifying suitable rock volumes for deposition as well as depth intervals for the
final repository facility has been outlined in /SKB 2009c/. This rationale has been used to establish
a depth interval where it is possible to find rock volumes that conform to the specific designpremises for deposition holes and deposition tunnels with regard to:
•
•
•
•
•
•
•

in situ temperature,
fracture frequency,hydrogeology considerations,spalling considerations,available space – site adaptation,
construction costs and environmental impact,
other considerations.

Applying the above rationale resulted in a depth range of 450 m to 500 m according to SER /SKB
2009c/. The in situ stress magnitude and the fracture frequency of gently dipping water-bearing fractures were the governing conditions. The reference repository depth i.e. the depth from the 0-level tothe roof of the highest located deposition tunnel is elevation –457 metres. The maximum depth of thetunnels in reference design is elevation –470 metres, i.e. where the transport tunnels (tunnel floor)
exit from the central area. The minimum and maximum depths are based on the tunnel inclinations
required for the drainage system.

4.2

Deposition area – placement of deposition holes

4.2.1 Thermal conditions
The layout of the deposition holes shall conform to the following design premise for thermal conditions
stated in Design premises long-term safety.
•

The buffer geometry (e.g. void spaces), water content and distances between deposition holes
should be selected such that the temperature in the buffer is <100°C.

The thermal dimensioning methodology presented in /Hökmark et al. 2009/ was applied to determine
the distance between deposition holes. The premises for the thermal dimensioning were: minimum
distance between deposition holes 6 m, fixed canister spacing, maximum thermal power in the canisters
1,700 W and fixed deposition tunnel spacing 40 m. The calculated increase in temperature from therock wall at mid-height of the canister to the buffer at top of the canister, where the highest temperature34

TR-10-18

in the buffer occurs, is presented in the Buffer production line, Section 4.4. Based on this the minimum spacing between deposition holes in the different rock domains was evaluated in /SKB 2009c/.
The reference design conforms to the design premise provided that the minimum centre-to-centre
spacing is 6.0 m in rock domain RFM029 and 6.8 m in rock domain RFM045.
Placing a deposition hole in rock with a very low thermal conductivity is not permitted. According tocurrent knowledge, volumes of rock with a very low thermal conductivity, i.e. amphibolite, are sparse
as well as detectable. The reference spacing between deposition holes does not take into account thefact that placing of deposition holes in rock with low thermal conductivity will be avoided, resulting
in loss of canister positions. However, it is recognised that there is good potential for refining thedesign and reducing the canister spacing once underground data becomes available.

4.2.2 Mechanical conditions
The following design premises for the mechanical conditions in deposition holes are stated in Designpremises long-term safety.
•

Deposition holes are not allowed to be placed closer than 100 m to deformation zones witha trace length longer than 3 km.

•

Deposition holes should, as far as reasonably possible, be selected such that they do not havepotential for shear larger than the canister can withstand. To achieve this, the EFPC criterion
should be applied in selecting deposition hole positions.

These design premises together with predetermined boundaries of the repository area governs thegross capacity of the final repository. A methodology for verifying the conformity of the reference
design to these design premises have been established by SKB /Munier 2006, 2007, 2010/.
Firstly, deposition areas must not be located within 100 m perpendicular distance from the boundaries
of modelled deformation zones with a 3 km trace length or equivalent size. Within the rock volume thatwill host the final repository, i.e. fracture domains FFM01 and FFM06, there are only four deformation
zones that are large enough to potentially require a respect distance. These are the three steeply dippingzones ZFMENE060A, ZFMENE062 and ZFMWNW0123, and the gently dipping zone ZFMA2, see
Figure 4-1. The reference layout was, in accordance with instructions given in /SKB 2009c/, fitted to a
3D model of deformation zones requiring respect distance.
Secondly, in order to mitigate the impact of potential future earthquakes, deposition hole positions
are selected such that they do not intersect discriminating fractures. Deposition positions must satisfy
the Extended Full Perimeter Intersection (EFPC) criterion /Munier 2010/. Theoretically, fractures withradii larger than about 60 to 200 m should be avoided, depending on the distance to the zone needing
respect distance, but since fracture sizes may be very hard to measure more robust criteria are needed.
For this purpose the EFPC criterion formulated in the following way is applied.
••

Fractures that intersect the full perimeter of the tunnel, and that also intersect the canister locationin the deposition hole are regarded potentially critical and all affected positions are rejected, see
Figure 4-2 a.
Additionally, to capture large fractures that do not intersect the full perimeter of the tunnel, any
fracture intersecting five or more deposition holes is regarded potentially critical and all affected
positions are rejected, see Figure 4-2 b.

There is uncertainty concerning the ability to predict the discriminating fractures at repository levelbased on surface mapping and core logging. As a result, the reference design layout was developedwith the aim of maximising the number of potential deposition positions, taking all design premises
and other constraints into consideration. The reference design has a gross capacity of 7,818 deposition hole positions and provides for a loss of deposition hole positions of approximately 23%. The
reference design acknowledges the fact that loss of deposition positions is an uncertainty but judgesthat the actual loss of positions is much smaller. Prospects are good in finding more efficient means ofidentifying discriminating fractures. Furthermore, the number of potential deposition positions can beincreased, for example by thermal optimisation or by utilising other potentially suitable rock volumes.

TR-10-18

35

Figure 4-1. Deformation zones with respect distances which impact the repository layout. Section at
repository depth (–470 m)1.

a)b)

Figure 4-2. Illustration of a) the FPC criterion (Full Perimeter Intersection criterion) and b) the EFPC criterion (Extended Full Perimeter Intersection criterion). Red positions are rejected, green positions are accepted.
1Modelldatabasen, 2007. Model: DZ_PFM_REG_v22.rvs. Version 0.3. Approved 2007-08-31, Modified 200711-29. Modeller: A. Simeonov. Simon ID: GEO_IZTKKYIL, Svensk Kärnbränslehantering AB.

36

TR-10-18

4.2.3 Hydrogeological conditions
The following design premises for the hydrological conditions in deposition holes are stated in
Design premises long-term safety.
•

The total volume of water flowing into a deposition hole, for the time between when the buffer is
exposed to inflowing water and saturation, should be limited to ensure that no more than 100 kgof the initially deposited buffer material is lost due to piping/erosion. This implies, according topresent knowledge, that this total volume of water flowing into an accepted deposition hole mustbe less than 150 m3.

•

Fractures intersecting the deposition holes should have sufficiently low connected transmissivity(specific value cannot be given at this point). This condition is assumed to be fulfilled if theconditions regarding inflow to deposition holes are fulfilled.

A rationale for dealing with the situation of rejection of planned deposition hole positions due tounacceptable inflow was established in /SKB 2009c/. To summarise, most of these positions are likely
to be screened out by the EFPC criterion, and the most likely situation is that very few additional
deposition holes will be lost due to high inflow. Note that the EFPC criterion according to /Munier
2006/ was applied for this purpose, i.e. deposition positions were rejected if they were intersected bywater conducting fractures also intersecting the full perimeter of the deposition tunnel independentlyof whether the canister location or any other part of the deposition hole was intersected. In the mostextreme case, an additional 6% could be lost due to high inflows /SKB 2009c, Table 2-13/.

4.3

Deposition holes

The following design premise for the excavated damaged zone in deposition holes is stated in
Design premises long-term safety.
•

Before canister emplacement, the connected effective transmissivity integrated along the full lengthof the deposition hole wall and as averaged around the hole, must be less than 10–10 m2/s.

Damages related to the excavation resulting in increased transmissivity along deposition holes can beeither the result of the applied method to excavate the holes, or a process governed by the mechanicalproperties of the rock and the redistribution of stresses around the excavated deposition hole. The
EDZ induced by the excavation activities is related to the performance and execution of the reference
method, and is discussed in Section 5.3.1.
The likelihood of spalling in deposition holes could be significantly reduced – if not eliminated – byaligning the deposition tunnels parallel to the maximum horizontal stress /Martin 2005/. A complete
description of spalling and the methodology used to assess the spalling potential can be found in/SKB 2009b, Appendix B/. According to the guideline given in /SKB 2009c/, the deposition tunnels
shall be aligned within ±30 degrees of the trend of the maximum horizontal stress to significantly
reduce the risk of spalling in deposition holes.
For deposition holes, the three dimensional elastic analyses showed that aligning the deposition tunnels
parallel to the maximum horizontal stress significantly reduces the maximum tangential stress on theboundary of the deposition hole. Moreover, the analyses indicated that such an alignment eliminates
the concentration in tangential stress near the top of the deposition hole and provides a more uniform
distribution of tangential stress along the deposition hole. For the “Most likely” stress model and fordeposition tunnels aligned greater than 30 degrees to the maximum horizontal stress, tangential stressconcentrations higher than current estimate of the spalling strength occurs in deposition holes. In such acase spalling occurs above the top of the canister.
With respect to the acceptable dimensions specified in Figure 2-1, a 5 cm overbreak relative to thenominal diameter of deposition holes is acceptable from the buffer block on top of the canister to thebottom of the deposition hole, i.e. from a depth of about 2 m below the deposition tunnel floor. (5 cm= acceptable radius 92.5 cm minus nominal radius 87.5 cm.) Additionally, in the part of the deposition hole where buffer is going to be deposited, the area of each horizontal cross section must notexceed the nominal cross section by more than 7.0%. The depth of spalling in deposition holes was

TR-10-18

37

Insignificant

Depth of spalling (cm) between 2 and 8 m

10

Minor

Moderate

Major

8

6

Acceptable
Most likely stress model (30 deg)

4

Unlikely maximum stress model (parallel)
2

0

0

500

1000

1500

2000

Number of deposition holes out of 6000

Figure 4-3. Loss of deposition holes for the “Most likely” stress model with the deposition tunnels at
30 degrees to the maxim horizontal stress and the “Unlikely maximum” stress model with the deposition
tunnel parallel to the maximum horizontal stress /SKB 2009b/.

analysed in /SKB 2009b/, see Figure 4-3. In the case of the “Most likely” stress model, the results
indicate that some 100–200 deposition holes (out of 6,000) would sustain a spalling depth (overbreak) that exceeds 5 cm, provided that the deposition tunnels are aligned between 0 and 30 degrees
to the maximum horizontal stress. For the “Unlikely maximum” stress model, the deposition tunnelmust be aligned parallel to the maximum horizontal stress, but the number of deposition holes that cansustain a spalling depth in excess of 5 cm is approximately the same.
Spalling in deposition holes due to excavation-induced stresses is permitted, but the final deposition
hole geometry must conform to the tolerances specified in the design premises imposed by the buffer.
Uncertainties related to the in situ stress conditions, rock properties and the capability to model theextent of spalling and related changes in transmissivity, restrict a verification of the reference design
at this stage. Means of reducing the remaining uncertainties related to spalling must be developed in
the next design, something which is facilitated by the design methodology presented in Chapter 3. The
contingency measure for reducing or eliminating spalling in deposition holes is to align the deposition
tunnels parallel to the maximum horizontal stress. In the event that spalling occurs on the boundaryof deposition holes, mitigation measures would need to be taken in order to increase the likelihoodof achieving conformity to the above design premises. Loose rock debris from localised spalling onrock walls in deposition holes would be scaled off. Scaling or rock fall-out will affect the dimensionsof deposition holes. Possible ways to adapt the installation of the buffer to the resulting geometry are
discussed in the Buffer production report, Section 4.7.2.
The design premises imposed for the deposition holes by the buffer are given in Table 2-2 and theresulting nominal geometry and acceptable variations are illustrated in Figure 2-1. The depositions
holes must conform to these design premises to achieve the required buffer density and a reliableinstallation of the buffer, see Buffer production report, Section 2.4.1. The specified acceptabledeviations in radii include all possible causes e.g. alignment, straightness, displacements and rockfall out. This is discussed in Section 5.3.2.

38

TR-10-18

4.4

Deposition tunnels

The following design premises for the excavated damaged zone in deposition tunnels are stated in
Design premises long-term safety.
•

Excavation-induced damage should be limited and not result in a connected effective transmissivity, along a significant part (i.e. at least 20–30 m) of the disposal tunnel and, averaged across thetunnel floor, higher than 10–8 m2/s.

The most likely orientation of the maximum horizontal stress is Azimuth 145 degrees. The variability isassessed to be ±15 degrees. Around 90% of the deposition tunnels in the reference design layout haveorientation Azimuth 123–127 degrees and the remaining tunnels are aligned in approximately Azimuth
140 degrees. The orientations of the deposition tunnels in the reference design conform to the guideline
given in /SKB 2009c/, stating that the deposition tunnels shall be aligned within ±30 degrees of the trendof the maximum horizontal stress. A three dimensional elastic stress analyses confirms this guideline/SKB 2009b/. The results indicate that the stress concentrations in deposition tunnels aligned between
0 degree and 30 degrees relative to the orientation of the maximum horizontal stress are below the spallingstrength used for the reference design. The results also suggest that stress concentrations in main tunnels aswell as in their crossings with deposition tunnels are below the currently assumed spalling strength.
It is stipulated in /SKB 2009c/ that the final decision on the alignment of deposition tunnels shalltake into account whether a prominent sub-vertical fracture set is aligned with the maximum
horizontal stress. When the strike of a fracture set forms a narrow angle with a deposition tunnel,
structurally related overbreak may occur and reduce the potential for maintaining an acceptable
excavation contour. Thus, a balance must be sought between the likelihood of spalling and thepotential for intersecting these sub-vertical fractures.
The design premises for acceptable dimensions and geometry imposed on the deposition tunnels by
the backfill are given in Table 2-3. The acceptable dimensions and geometry of the deposition tunnels are illustrated in Figure 2-2. The deposition tunnels must conform to these design premises toachieve the specified backfill geometrical configuration and related installed density and to achievea reliable installation. The EDZ induced by the excavation activities is related to the performanceand execution of the corresponding reference method. This is discussed in Section 5.2.1.
The design premises imposed for the deposition tunnels by the plug are given in Table 2-4. They
comprise the construction of a recess for foundation of the concrete plug and anchoring of structures
for the installations, as well as acceptable inflow and strength of the rock mass in the area where
the plug shall be installed. The construction of the recess is discussed in Section 5.2.5. For the otherdesign premises imposed by the plug there are no specifications so far. For rock reinforcement andgrouting the approaches discussed in Section 4.6.1 and 4.6.2 are applied.

4.5

Other underground openings

The following design premises for the excavated damaged zone in the underground openings in thecentral area, ramp, shafts and tunnels other than deposition tunnels are stated in Design premises
long-term safety.
•

Below the location of the top sealing, the integrated effective connected hydraulic conductivityof the backfill in tunnels, ramp and shafts, and the EDZ surrounding them, must be less than
10–8 m/s. This value need not be upheld in sections where e.g. the tunnel or ramp passes highly
transmissive zones. There is no restriction on the hydraulic conductivity in the central area.

The occurrence of spalling in the access ramp and the transport tunnels were not analysed separately.
However, the consequence of spalling from a long-term safety point of view is insignificant. Below
the top seal the orientation and shape of the ramp can be modified to mitigate spalling, if necessary.
Elastic stress analyses for the rock caverns in the central area central area was carried out using a
2D-modell /SKB 2009b/. The results suggest that when the central area is oriented between 0 degrees
and 30 degrees relative to the orientation of the maximum horizontal stress, stress concentrations in
the caverns are below the spalling strength for the reference design.
The EDZ induced by the excavation activities is related to the performance and execution of thecorresponding reference method. This is discussed in Chapter 5.
TR-10-18

39

4.6

Engineered and residual materials

The following design premises for engineered and residual materials left in the final repository, when
the installation of buffer is performed or the underground openings are backfilled or closed, are statedin Design premises long-term safety.
For deposition tunnels:••

only low pH materials (pH<11),no continuous shotcrete.

For boreholes, shafts and ramp, rock caverns and tunnels other than deposition tunnels:•

only low pH (<11) materials are allowed below the level of the top seal.

Engineered materials left in the final repository consist of materials for grouting sealing and rock reinforcement. Cement is used in shotcrete, for embedding various support elements and in grout mixes
for sealing purposes. In addition, there are residual materials from the operation of the final repository
facility that will remain after decommissioning and preparations for installation of buffer, backfill or
closure. For these the following design premise is stated in Design premises long-term safety.
•

Other residual materials must be limited – but the amounts considered in SR-Can is of noconsequence.

The assessed amounts of engineered materials from rock support and grouting activities and theamounts of residual materials are presented in Section 4.6.3.
In addition to the material the following applies to sealing of deposition tunnels:•

continuous grouting boreholes outside tunnel perimeter should be avoided.

General engineering guidelines /SKB 2009c/ were considered in the reference design with regard torock support issues and sealing. These guidelines cover feasibility for both construction and deposition,
and are highlighted below.
•••

The deposition holes shall be located in massive or sparsely fractured rock.
The central area can be located in any rock mass suitable for constructing large caverns.
The repository facility layout should minimise stress concentrations on the perimeter of theunderground excavations (deposition holes and deposition tunnels), unless it can be shown thatsuch stress concentrations do not cause spalling.

A rationale for identifying suitable rock volumes on the basis of the above guidelines was outlined
in /SKB 2009c/. The underground openings in the reference design and thier response to excavation
have been characterised in accordance with the following principles.
An engineering description of the rock mass was established based on the site description, /SKB
2008/. This engineering description considers the rock domains, fracture domains, major deformation
zones, ground water conditions and in situ stress conditions. It also incorporates parameters that are
required to provide an engineering description of the rock mass. The product of this description is an
identification of a number of ground types and of site-specific conditions that have been evaluated in
the reference design. Three different ground types were defined based on the current knowledge of thegeological setting.
Ground types are the basis for evaluating the rock mass behaviour of each underground opening after
excavation without considering the effect of rock support or sealing. The ground behaviour also considers the influencing factors such as the relative orientation of relevant discontinuities to the excavation,
ground water conditions and in situ stresses.

40

TR-10-18

4.6.1 Rock support in underground openings
To facilitate estimates of quantities of ground support for the reference design, guidelines are given in/SKB 2009c/. They are based on extensive underground construction experience and outline which
categories of rock support, e.g. rock bolts and shotcrete that may be suitable to use in the foreseen
ground types. These categories are designated support types.
The rock caverns in the central area and transport tunnels connecting deposition areas to each other are
not aligned parallel to the NE trending fracture set, which may be unfavourable from a rock mechanics
point of view. This orientation will reduce the need for bolting as well as the likelihood of structurallyrelated overbreak. The results from the stress analyses for the central area /SKB 2009b/, indicate thatthe central area is located in a rock volume suitable for construction of large caverns.
The ramp will have tunnel sections which are aligned parallel to the NE trending fracture set. On
the repository level, the main tunnels will also be parallel to the NE trending fracture set. The reference design includes quantities of rock support specifically aimed at reducing structurally-related
overbreak to an acceptable level.
Using the “Most likely” stress model /SKB 2009b/ the in situ stress conditions at the depth of therepository are not expected to be sufficient to cause stress-induced stability problems – spalling – inthe underground openings. However, there is uncertainty regarding this design parameter. In order toprevent minor spalling from being a occupational safety issue, roof support with shotcrete is includedin the reference design for all underground openings except in the deposition tunnels where wire meshshall be used if necessary.

4.6.2 Grouting measures in underground openings
The design premises for acceptable inflow imposed on the deposition tunnels by the backfill are
given in Table 2-3. The deposition tunnels must conform to these design premises to achieve a
reliable installation of the backfill.
In order to limit the water inflows as much as possible, the following general engineering principles
were considered in the reference design /SKB 2009c/.
••

The access tunnels (ramp) and shafts should be located to minimise the potential for large
groundwater inflows.
The layout for the ramp and shafts should be oriented so that the intersection lengths with majorwater bearing zones are as short as possible.

The reference design also contains an assessment of the extent to which grouting must be used toconform to the specified acceptable inflows. In the specifications used to establish the reference
design, grouting of the rock surrounding the underground openings at repository level were limited tousing cement-based grout ahead of the advancing excavation /SKB 2007/, i.e. pre-grouting. Available
results indicate that the sealing efficiency of cement-based grouting at the repository level will be
sufficient and that the reference design conforms to the specified inflow. However, for certain fracturesand deformation zones in deposition tunnels it may not be practical to use cement-based grouts. While
there is acceptable confidence that the number of occurrences for such conditions is relatively few,
there is uncertainty regarding the level of effort for controlling the groundwater inflows under suchcircumstances. In order to reduce this uncertainty, options were included in the references designfor the use of solution grouting, e.g. such a method tested at the Äspö Hard Rock Laboratory (HRL)/Funehag 2008/, see Section 5.2.4.
In fracture domain FFM02, located within the upper 100–200 m of the rock, the rock has a relatively
high frequency of transmissive fractures. Extensive grouting measures may be needed for the accessexcavations that penetrate this fracture domain. The reference design acknowledges that detailed
grouting plans can only be prepared once the detailed site specific information is obtained.
In fracture domains FFM01 and FFM06, the frequency of transmissive fractures is generally low anddecreases with depth. The grouting of different underground openings below a depth of 200 m canbe carried out as selective pre-grouting, with probe hole investigations, when passing deformation
zones and where discrete water-bearing fractures are encountered.

TR-10-18

41

Below a depth of approximately 400 m, the observed frequency of flowing features is very low andgrouting of flowing fractures and zones will be localised and not result in continuous grouting holes
outside the deposition tunnel perimeter. The cumulative density function of transmissivity values in
20 m long sections indicates that on average, less than 2% of the 20 m sections between deformation
zones will require grouting /SKB 2009c, Section 2.5/ and that each deposition tunnel will on averageintersect two deformation zones that will require pre-grouting.
Decisions to grout will be based on probing inside the tunnel perimeter. However, construction experience indicates that detecting these fractures by means of traditional probe hole drilling from thetunnel face may be difficult, particularly if the water-bearing fractures have relatively small apertureswith channelised flow. Due to the difficulty in identifying individual water-bearing fractures, any
point leakages of >0.1 l/min remaining in deposition tunnels will be sealed by post-grouting.
The design premises do not restrict the use of grouting around deposition holes. However, grouting was
not considered in the reference design as a means of reducing inflow in potential deposition holes. The
bottom holes of grouting fans in deposition tunnels will be drilled inside the tunnel contour to prevent
grouting holes from intersecting potential deposition hole positions. The grouting fans located in
deformation zones will not be constrained since deposition holes are not allowed in deformation zones.
The ventilation shafts in the deposition area that connect to the ground surface will be constructedusing raise-boring techniques. Grouting in these shafts will be carried out before excavation (raise
drilling) begins, if required. This grouting would require long boreholes with minimum deviation.
Boreholes could be drilled from the surface and from underground.

4.6.3 Quantities of engineered and residual materials
Engineered materials originating from rock support and grouting activities will remain in the final
repository after decommissioning and closure of the repository facility. Residual materials from theoperation of the final repository facility will also remain in the final repository.
The structural elements included in the rock support are rock bolts, shotcrete, fibre reinforcement andwire mesh. It is assumed that shotcrete with its additives, aggregates and fibre reinforcement as wellas wire mesh will remain on the rock surfaces of the underground openings and that rock bolts willremain in the rock walls and roofs of the underground openings. The bolts, fibre reinforcement andwire mesh mainly consist of iron. The assessed material quantities used for ground support left in the
different kinds of underground openings are given in Table 4-1 /SKB 2009b/. Table 4-1 includes total
masses and volumes as well as relative quantities expressed in kg/m3.
The assessed quantities from grouting activities are given in Table 4-2 for the different functional
areas /SKB 2009b/. The estimated quantities concern cement, silica fume, silica sol and additives.
The total number of grout holes and the corresponding drilled metres are also given.
The quantities of grout presented in Table 4-2 includes the grouting in probe holes, pre-grouting at
the tunnel face, post-grouting and cut-off grout curtains for shafts and for the top part of the ramp
located in fracture domain FFM02. The grouting methodology comprises three different cementbased grout mixes with a low pH. The average quantity of cement plus silica fume in 1 m3 of grout
mix is 790 kg. The cement quantities used for plugging the grout holes after grouting is completed
are not included in Table 4-2. This additional cement quantity has been estimated to 1,000 tonnes.
The assessed quantities of residual materials from the operation of the final repository facility are
given in Table 4-3 for the different underground openings /Lindgren et al. 2009/. The inventory ofresidual materials concerns normal operation and does not include e.g. accidents, fire or sabotage.
The assessed quantities are based on the assumption that the underground openings are decommissioned
and cleaned so that 1% of the materials brought into the repository for the operation will remain in therepository. The largest amounts of residual materials are steel and rust from rock bolts securing ventilations equipment and cables, residuals from concrete constructions such as firewalls, pumping pits androadways in the facility and nitrate salts from the explosives. The quantities of residual materials, otherthan the bottom plate, left in the deposition holes are very limited, even too small to be quantified.
The materials and their amounts given in Table 4-3 have been compared to the materials and amounts
presented in the initial state report for SR-Can. No new materials are identified and the estimatedamounts are comparable to those presented in SR-Can.
42

TR-10-18

Table 4-1. Compilation of the material and quantities expected to be used for ground support indifferent parts of the repository /SKB 2009b, Table 6-6/.
Subsidiary material

kg/m3

Ramp/access
[ton]

[m3]

Central area,
Deposition area, includincluding ventilation ing SA012 and SA022
[ton]
[m3]
[ton]
[m3]

Rock Bolts
Rock bolts (l=3 m, d=25 mm)

4

27

52

182

Wire mesh (1.7 kg/m2)

96

Fixing bolts (29,329 pcs)

28.2

Rock Bolt Grout
Cement

340

15

7

28

13

98

47

Silica

226.7

10

5

19

9

65

31

Water

266.6

12

12

22

22

77

77

Glennium 51

4

0.2

0.2

0.3

0.3

1

1

Quarts filler

1,324

57

29

109

54

381

191

Shotcrete

Water

158

239

239

340

340

744

744

Ordinary Portland cement CEM I 42.5

210

318

151

452

215

989

471

Silica fume

140

212

101

301

143

659

314

Coarse aggregate (5–11)

552

836

492

1,187

698

2,600

1,529

Natural sand (0–5)

1,025

1,552

913

2,205

1,297

4,227

2,839

Quarts filler (0–0.25) or Limestone
filler (0–0.5)

250

379

189

538

269

1,177

589

Superplasticiser “Glennium 51” from
Degussa

3

4.5

4.5

6.5

6.5

14

14

Air entraining agent “Sika AER S”

2.5

3.8

3.8

5.4

5.4

12

12

Accelerator “Sigunit” from Sika or
AF 2000 from Rescon

7%1

0.1

0.1

0.2

0.2

0.3

0.3

1) Tests performed have given values between 4 and 10%. An average value of 7% was however chosen for thesecalculations.
2) SA01 and SA02 are ventilation shafts in the peripheral parts of the deposition areas.

Table 4-2. Estimated quantities of grout materials and drilling that remain in the rock mass after
excavation of the different underground openings (based on /SKB 2009b, Table 7-4/).
Element

Material

Ramp/Shafts (ton) 1) 2 ) Central Area (ton) 1)
min
max
min
max

Deposition Area (ton) 1)
min
MaxCement grouting

Water

350

1,360

3

10

110

440

330

1,310

3

8

100

400

Silica Fume 4)

460

1,790

4

11

140

550

Super Plasticiser 5)

23

90

0.2

0.5

7

30

Silica Sol

105

410

3

9

160

640

NaCl solution

21

85

0.6

2

30

130

Volume of grout (m3)

910

3,580

10

30

405

1,620

Drilling

Number of holes

7,980 pcs

300 pcs

17,160 pcs

Drilling meter

205,000 m

6,000 m343,000 m

Portland

Solution grouting

3)1) Based on “type” hydraulic conditions (Ktyp).
2) Incl. the Exhaust shafts SA01 and SA02.
3) Sulphate resistant Ordinary Portland cement with d95 on 16 µm, type Ultrafin 16 or equivalent.
4) Dispersed silica fume, microsilica with d90=1 µm type Grout Aid or equivalent. The density is to be between
1,350–1,410 kg/m3 and 50% ±2% of the solution is to consist of solid particles, see Appendix C in /SKB 2009b/.
5) Super plasticiser, naphthalene-sulphonate based, density about 120 kg/m3, type SIKA Melcrete.

TR-10-18

43

Table 4-3. Estimated quantities of residual materials (in addition to engineered materials given
in Table 4-1 and Table 4-2) that remain in the rock underground openings at closure of the final
repository /Lindgren et al. 2009/.
Quantities of residual materials in the final repository (kg)
Deposition Deposition Main andCentralRamp andholes
tunnelstransport tunnels area
shaftsMaterial

Detonators with leaders

Zinc

*

5

3

0.6

Plastic

*

80

40

9

20

Explosives

NOx

*

7

4

1

2

Nitrate salts

*

2,000

1,000

200

400

Bolts

Steel

*

50,00040,00010,00020,000Concrete0030,0008,000

20,000Roadways

Concrete

0

0

2,000

600

1,000

Asphalt**

0

0

0

0

500

Concrete constructions

Concrete

*

3,000

2,000

600

1,000

*

1

5

1

3

NOx

*

7

30

9

20

Tyre wear
Exhausts

Particles
Detergents and degreasing
compounds

1

*

0

0

0

0

0

0

0

*

0

Hydraulic and lubrication oil

*

200

50

10

20

Diesel oil

*

*

*

*

*

Battery acid

*

*

*

*

*

Metal chips and hard metal

*

5

1

0.3

1

Wood chips

Wood

*

10

0.6

0.2

0.3

Corrosion product

Rust

*

4,000

200

50

90

Urine

Urea

*

6

1

0

0.6

Other human waste

Organics

*

60

10

3

6

Ventilation air

Organics

*

10

5

1

2

* too small to quantify** in the ramp but not in the shafts

44

TR-10-18

5

Reference methods

5.1

General basis

The design premises in Design premises long-term safety and the design premises imposed by the
buffer and backfill together with the design considerations presented in Section 2.2.2 result in designpremises for a number of methods used for the construction of the underground openings. This chapter
presents the reference methods for the construction. SKB regards the reference methods as technicallyfeasible, however, some methods need to be further developed before the construction of the repository
facility commences.
The used technology, the operational aspects and the environment in which the reference methods areoperated, are all possible sources of uncertainty relative to the performance of the reference methods.
The conformity to the design premises will be handled as part of the observational method and the development of quality control and assurance procedures as outlined in Section 3.4. A general description of
methods and approach to monitor the performance of the reference methods is given in /SKB 2010/.
Within the framework of the observational method the predicted performance of the reference methods
need to be fully established before they are put in operation to construct the underground openings ofthe repository facility. Moreover, before a reference method can be considered as operational, parameters and criteria (threshold levels) that shall be used to predict the performance must be established.
Observable and quantifiable parameters with potential for predicting the performance of the reference
methods are outlined in the following sections.

5.2

Reference methods used for the construction ofdeposition tunnels

The reference method for excavating the deposition tunnels is drill and smooth-blasting techniques.
The design premises for the deposition tunnels related to their function in the KBS-3 repository are
given in Table 2-1 and the design premises imposed by the backfill are given in Table 2-3. Prior to theinstallation of the backfill the conformity of the connected transmissivity, the amount and compositionof engineered and residual materials in the tunnel, the inflow and geometry to the design premises shallbe verified, and the tunnel shall be prepared for installation of the backfill, see Section 5.2.6 and the
Backfill production report, Section 5.4.3.

5.2.1 The excavation damaged zone using drill and blast techniques
In Design premises long-term safety it is stipulated that the contribution from the EDZ to the connected effective transmissivity along and across deposition tunnels shall be limited. The appearanceof an EDZ is typical in underground openings excavated by drill and blast. /Bäckblom 2008/ statesthat many studies correlate damage with the concentration of explosives used. Equally important are
the accuracy and precision in drilling the blast holes, and using exact ignition times, e.g. by utilising
electronic detonators /Ericsson et al. 2009/. In addition, local geological conditions and the rock stressenvironment will influence the resulting EDZ /Jonsson et al. 2009/.
Whether EDZ is continuous or discontinuous over adjacent blast rounds is of importance, because if the
EDZ’s are connected between rounds there is potential for an addition to the natural connected transmissivity. Based on experiences from the excavation of the TASQ tunnel at the Äspö HRL /Olsson et al.
2004/ it was noted in SR-Can that it is possible to design and control the drilling and blasting of tunnels
such that continuous fracturing along the axial direction of the tunnel will not develop. This notion
has been demonstrated at the Äspö HRL in the TASS tunnel using smooth-blasting techniques /Olsson
et al. 2009, Ericsson et al. 2009/. Results from the TASS tunnel show that proper control of drilling andblasting procedures result in blast-induced fractures that are dominantly radial in direction and that such
fractures are not continuous over any significant distance along the axial direction of the tunnel.

TR-10-18

45

A reasonable value for the hydraulic conductivity of the damage zone is in the order of 10–8 m/s. Thismagnitude has been obtained during several tests in crystalline rocks, where the excavation was ofgood quality and measured by integrating measurement under saturated conditions along the tunnel
floor /Bäckblom 2008/. Point observations of the hydraulic conductivity have provided both lowerand higher individual results. This is due to the natural variability of the rock properties as well as tothe fact that damage is correlated to the amount of explosives. The latter varies along the peripheryof the opening and also along the longitudinal section of the tunnel.
The properties of a damaged zone surrounding an underground opening change if spalling has occurred.
The results of the major experiments suggest that the hydraulic conductivity of such a zone will be in theorder of 106 m/s and that it extends a couple of decimetres into the rock surrounding the undergroundopening /Bäckblom 2008/.
The parameters that have potential to predict and verify the performance of the reference method andfor which criteria will be determined are the amount of explosives close to the periphery, accuracy andprecision in drilling the blast holes, distance between blast holes and accuracy and sequencing of theignition. The reference method will include calibration procedures to accommodate the site specificconditions that deviate from the most probable conditions, e.g. by adjusting the drill pattern or bychanging the type of detonators.
Monitoring and control programmes

SKB plans to develop several procedures for verifying that the EDZ conforms to the design premises.
Primarily quality control and assurance procedures included in the control programme will be applied
to control and inspect that the drilling, charging and ignition sequences are properly executed. The
influence from rock conditions on EDZ will be evaluated within the framework of the observational
method and the associated monitoring programme, i.e. combining results from geological characterisation, geophysical techniques and geological modelling.
The completed deposition tunnels are visually inspected to identify any occurrences of localised
blast damage or spalling. The potential to conform to the design premises for connected effective
transmissivity can be improved by removing loose rock debris on the rock walls. This mitigation
measure requires that a criterion is established that define the accepted intensity of loose rock debris.
The reference design includes mitigation measures to reduce the risk of spalling as the deposition
tunnels are aligned sub-parallel to the major horizontal stress, see Section 4.3.

5.2.2 Geometrical tolerances
Acceptable geometrical tolerances for the deposition tunnels are imposed by the backfill, see Figure 2-2.
The constraints concern the total volume of the excavated tunnel, the maximum cross-sectional area andcavities in the tunnel floor. Moreover, underbreak is not allowed, i.e. the rock contour may not protrude
inside the nominal tunnel profile.
Smooth-blasting techniques were demonstrated at the Äspö HRL. The demonstration included sevenexcavation stages. The intermediate results from four stages, or 12 blasting rounds have been reported/Malmtorp et al. 2009/. The results showed that proper control of drilling and blasting resulted in conformance to the geometrical tolerances for maximum allowable cross-section and excavated volume.
The rock surfaces in tunnels excavated by drill and blast are rough and it can not be excluded that small
volumes of rock will protrude inside the nominal cross-section, i.e. underbreak.
The results of blasting rounds 6 to 12 have been used to estimate the installed backfill density at theinitial state, see Backfill production report, Section 6.1.4. For this purpose the as-built volumes of
the tunnel are compiled in Appendix A.
A look-out angle of 250 mm was found to provide sufficient space for the drilling equipment but did not
eliminate all occurrences of underbreak. It is therefore reasonable to estimate the backfill density basedon that drilling of the contour holes is made with a look-out angle of 250 mm. Based on the experimental
data the average excavated volume per round was assessed to be approximately 18% larger than thenominal volume i.e. well within the acceptable limit of 30% larger than the nominal volume.

46

TR-10-18

The parameters that have potential for predicting and verifying the performance of the reference method
and for which criteria will be determined are related to control and inspections of the precision andaccuracy in drilling of the blast holes. This applies in particular to the blast holes along the perimeterof the tunnel (contour holes) and to the nearest row of blast holes (stoping holes). Precision applies topositioning at the start and completing the drilling at the attempted end location. Accuracy applies todrilling parallel holes and achieving the attempted look-out angle of the drill holes. Moreover, meansof detecting and removing underbreak will be an integral part of the reference method. The reference
method will include calibration procedures to accommodate the rock conditions that deviate from themost probable conditions. For example an increasing tendency in occurrences of underbreak can behandled by adjusting the drill pattern.
Control programme

There are suitable methods and instruments for inspecting the geometry of deposition tunnels, e.g. laser
scanning and geodetic methods. SKB will develop a procedure to inspect that the geometrical tolerances
in deposition tunnels conform to the design premises. The control programme for drilling, charging andignition that will be developed for EDZ is applicable. The geometrical tolerances after blasting will beinspected by one or a combination of the measurement methods mentioned above. In addition SKB will
customise a modelling tool that can evaluate the relevant geometrical properties of the deposition tunnel.
Nonconformity to the specified maximum cross-sectional area and maximum volume is foreseen to
be mitigated. Shotcrete will be applied locally where required, to smoothen out the rock surface due
to any irregularity or rock fall out. Underbreak will be removed by using mechanical equipment. The
final contingency action would be to disqualify the deposition tunnel in the event of nonconformities
to the geometrical tolerances that cannot be mitigated. A deposition tunnel that has been disqualified
will be backfilled in the same way as a main tunnel, see the Closure production report.

5.2.3 Tunnel floor contour
Acceptable geometrical tolerances for the deposition tunnel floor are imposed by the backfill. SKB
will develop a reference method that can provide a tunnel floor contour that conforms to the designpremises imposed by the backfill. A feasibility study of potential methods is ongoing in which smooth
blasting techniques and wire sawing techniques, or combinations thereof, are assessed.
Control programme

The control programme that will be developed for geometrical tolerances is applicable, see Section 5.2.2.

5.2.4 Grouting techniques and grouting results
Acceptable inflow conditions for deposition tunnels are imposed by the backfill. The current reference
method for sealing the rock surrounding the underground openings is grouting the rock beyond the
excavation face, i.e. pre-grouting, using low pH cement /SKB 2007/.
Suitable grouting measures were assessed for the reference design /2009b/. This evaluation pointed
to that grouting between deformation zones at the repository level will be very limited. When grouting is required, it is anticipated that cement based grouts will be adequate to achieve the required
sealing efficiency. However, in some situations the transmissivity of a fracture could be so low thatreaching the required sealing efficiency may not be practical with cement based grouts. In order toconform to the design premises the use of solution grouting may be required. The application ofsolution grouting under such conditions is considered to be new technology.
Intermediate results from testing solution grouting with silica sol at the Äspö HRL have beenreported in /Funehag 2008/. The results from the demonstration showed that the expected sealing
efficiency can be achieved when detailed design procedures /Fransson 2008/ are combined withproper control of the grouting operation. The detailed design included investigation boreholes andhydrogeological characterisation of the rock volume that was going to be grouted. The grouting
operation included procedures for controlling grout pressures and rheological grout properties andverifying them relative to the criteria established in the detailed design.
TR-10-18

47

SKB will continue the development of the reference method, i.e. the design methodology and theoperational aspects. Parameters and criteria for predicting and verifying the performance of the reference method will be established for specific purposes. For example potential parameters that relates
to the rock conditions and to the sealing efficiency are the distribution of fracture apertures, groutpressure in combination with rheological properties of grouts and consumed volume of grouts. The
latter parameters can be quantified and implemented as stop criteria in the operations.
The final testing and means of calibrating the reference method will be undertaken in representativerock conditions and with grout material and grouting equipment that will be used in operations at therepository level.
Monitoring and control programmes

SKB will develop several procedures for verification of that the inflow in deposition tunnels conforms to
the design premises. The input to detailed design will be obtained within the framework of the observational method and the associated monitoring programme, i.e. combining results from geo-hydrologicalcharacterisation and geological modelling in different scales. The model that refers to “tunnel” scale
comprises geo-hydrological characterisation of at least one investigation hole drilled along the planned
location of the deposition tunnel. A control programme will be applied to verify the performance of thegrouting operation.
After completing the excavation it is relatively straightforward to inspect the inflow. Normally, measuring weirs are constructed across the tunnel floor to measure the inflow. Monitoring results have a highreliability in stationary conditions and can be used to determine inflows along the full length of thetunnel or between weirs. It is foreseen that the monitoring programme will be in place until the deposition
activities commences.
If the inflows do not conform to the design premises, the contingency action will be post-grouting. Postgrouting will be carried out using cement grout or solution grouting. The ultimate contingency action
would be to disqualify the deposition tunnel if the results from mitigation measures are inadequate.

5.2.5 Recess for the plug in deposition tunnels
The design premises for deposition tunnels imposed by the plug installed at the end of the tunnel
after it has been backfilled are found in Table 2-4. The related rock engineering work includes the
excavation of a recess for anchoring of the concrete plug, see Figure 5-1. The required recess andanchoring can be prepared by applying conventional technique.
5.2.6 Preparation of deposition tunnels
The preparation of the deposition tunnels is carried out before installation of buffer and depositionof canisters is initiated in the tunnel. The preparation of deposition tunnels comprises the following
activities, see Backfill production report, Section 5.4.3.
•
•
•
•
•
•
•

48

The rock walls of the tunnel are inspected and if necessary scaling and rock bolting are executed.
Roof bolts that reach inside the nominal cross section of the tunnel are cut behind the washer.
The tunnel is cleaned and emptied of equipment from earlier activities.
The tunnel bottom is cleaned from gravel and other materials and inspected.
The inflow to the tunnel is inspected.
Scanning of the rock walls is carried out to determine the tunnel volume, the tunnel contour andthe geometry of the bevels.
Temporary ventilation, electric supplies and lighting are installed in the tunnel.

TR-10-18

Grouting pipes

Concrete beams Backfill end zone

Drainage

Concrete plug

Watertight seal

FilterFigure 5-1. Schematic illustration of a reinforced plug that is anchored in a recess in the rock around thedeposition tunnel.

5.3

Reference methods used in construction of deposition holes

The reference method for excavating the deposition holes are full-face down-hole drilling techniques.
The design premises for deposition holes related to their function in the KBS-3 repository are foundin Table 2-1and the design premises imposed by the buffer are found in Table 2-2. Prior to the installation of the buffer the conformity of the fractures intersecting the deposition hole, the inflow, theconnected transmissivity and geometrical tolerances to the design premises shall be verified and thedeposition hole prepared for installation of the buffer, see Buffer production line, Section 5.4.3.

5.3.1 Excavation damaged zone using mechanical excavation techniques
In Design premises long-term safety it is stipulated that the contribution from EDZ to the connected effective transmissivity in deposition holes must be limited. In Design premises long-term
safety it is foreseen that the deposition hole conforms to the design premises for connected effective
transmissivity (less than 10–10 m2/s, see Table 2-1) if it conforms to the conditions for acceptableinflow. However, as discussed in Section 4.3 the reference design does not rule out the likelihood of
local spalling due to local heterogeneities of the rock properties and the horizontal stress direction.
In underground openings excavated with mechanical excavation methods it is possible to achievea EDZ that is limited to a few centimetres into the rock surrounding the excavation and with ahydraulic conductivity that is in the order of 10–10 m/s /Bäckblom 2008/. These properties are valid
in rock conditions where spalling has not occurred. Hence the full-face down hole drilling method
can be expected to create very little damage to the surrounding rock walls. The resulting connected
effective transmissivity after excavation will therefore be governed by the connected transmissivityof natural fractures that intersect the deposition holes and the occurrence and intensity of spalling.

TR-10-18

49

Control programme

Currently there is no reliable method that can quantify the connected effective transmissivity. Geo­physical techniques have been used to characterise EDZ, however, none of these are by themselves
sufficient for assessing the intensity and extent of the EDZ. Currently it is foreseen that the deposition holes conforms to the design premise for the connected effective transmissivity if it conforms
to the conditions for acceptable inflow. An inflow criterion will be established based on the designpremise in Design premises long-term safety stipulating the maximum volume of water that isallowed to enter the deposition hole after the buffer is exposed to water until it is saturated.
A visual inspection of the completed deposition hole is necessary in order to rule out the occurrenceof spalling. Should localised spalling occur, the potential to conform to the design premises for connected effective transmissivity can be improved by removing loose rock debris on the rock walls. This
mitigation measure requires that a criterion that defines the accepted intensity of spalling is established.
The final contingency action will be to reject and backfill the deposition hole.

5.3.2 Geometrical tolerances
Acceptable geometrical tolerances for deposition holes are imposed by the buffer. The design premises
concerns the minimum diameter, minimum and maximum radius as well as maximum cross-sectional
area. This will impose constraints on the performance of the reference method in terms of the resulting
diameter and straightness of the deposition hole. Constraints are also imposed on the stability of rockwalls as the depth of any rock fall will influence the resulting dimensions of the deposition hole.
Further, the bottom of the deposition hole must be flat, the reference method to achieve a flat bottom is
to install a bottom plate, see Section 5.3.6.
Thirteen experimental deposition holes were excavated to full depth by means of full-face down hole
drilling at the Äspö HRL. Six of those deposition holes were located in the Prototype Repository. A
presentation of the works and the results is given in /Andersson and Johansson 2002/. The objective
was to demonstrate the technique for full-face down hole drilling of large vertical holes in granitic
rock. The geometrical tolerances that was specified for the demonstration, differs slightly from those
imposed by the buffer given in Table 2-2 in this document. However, the results from the demonstration showed that the drilling accuracy was acceptable. Moreover, the dimensions of the deposition
holes in the Prototype Repository conform to the design premises imposed by the buffer.
The results from the Prototype Repository has been used for the purpose of estimating the installedbuffer density at the initial state, see Buffer production report Section 6.1.4. The parameters usedin the assessment are the as-built diameter and straightness of the deposition holes. The data used for
estimating the installed buffer density are compiled in Appendix B.
SKB has initiated a feasibility study for developing the next generation of full-face down hole drill rigs.
New technology will be introduced improving the already acceptable performance of the reference
method. The number of deposition holes that will be drilled exceeds 6,000 and maintaining consistency in the drilling precision and accuracy is a key factor. Based on the demonstration some general
conclusions can be drawn regarding key parameters and associated criteria that govern deposition holestraightness, diameter and cross-sectional area and their tolerances. It was found that two types of variability exists; variability relative to the scale of individual cross-sections and variability relative to thescale of individual deposition holes. The variability of the mean diameter for individual cross-sections
in a deposition hole can be expected to be larger than the variability of the mean diameter for individual
holes. It was also found that the theoretical centre point for individual cross-sections deviated withthe depth of the deposition hole relative to a reference line between the theoretical centre point at thebottom of the hole and the theoretical centre point at the top. The maximum deviation is expected to beless than 10 mm, see Appendix B.
Control programme

There are suitable methods and instruments for inspecting the dimensions of deposition holes, e.g.
laser scanning and geodetic methods. SKB will develop a procedure for verifying that the geometricaltolerances in deposition holes conform to the design premises. Primarily quality control and assurance
procedures will be applied to inspect the positioning and alignment of the drill rig as well as the50

TR-10-18

conditions related to the drilling operation, e.g. checking cutter conditions. The resulting geometry after
drilling will be inspected by one or a combination of the above measurement methods. A visual inspection of the completed deposition hole is also necessary in order to rule out the occurrence of spalling. In
addition, SKB will customise a 3D modelling tool that can evaluate the relevant geometrical propertiesof the deposition holes. Any deposition hole that do not conform to the geometrical tolerances shall berejected and backfilled.

5.3.3 Acceptable inflow
Acceptable inflow to deposition holes is stated in Design premises long-term safety. Further, according to Design premises long-term safety, grouting of deposition holes can be considered as long as
the results are compatible with the long-term safety design premises. This implies that only verticalgrouting holes which are fully located inside the planned deposition hole are acceptable. However,the current reference design does not consider grouting as a means to improve deposition holes withunacceptable inflows. Furthermore, it is foreseen that most of the planned positions for deposition
holes having a potential for unacceptable inflows are likely to be screened out by the EFPC criterion,
see Section 4.2.2.
SKB will develop a reference method for the selection of deposition hole positions with acceptableinflows. There are several parameters and associated criteria that have potential for predicting andverifying the performance of such a reference method. For example geo-hydrological characterisation can be carried out and inflows can be measured both in the pilot hole that will be drilled in theplanned deposition hole position, and in the deposition hole after excavation.
Monitoring and control programmes

SKB will develop a procedure for verifying that the inflow in deposition holes will conform to thedesign premises. The planned locations of deposition holes will be decided in the detailed design.
Input to adjusting or verifying the detailed design will be obtained within the framework of theobservational method and the associated monitoring programme, i.e. by combining results fromhydrogeological characterisation and geological modelling in different scales. The model that refers
to deposition hole-scale comprises geological mapping of the deposition tunnel and hydrogeologicalcharacterisation of the investigation hole which is drilled at the planned location of the deposition hole.
Inflow criteria for pilot holes and deposition holes will be established based on the design premises
stated in Design premises long-term safety. The design premises stipulate the maximum volume ofwater that is allowed to enter after the buffer is exposed to water until it is saturated. It is foreseen thatthe inflow to excavated deposition holes will be monitored until the completion of the installation of thebuffer. Any deposition hole that do not conform to the design premise will be rejected and backfilled.

5.3.4

Methodology for accepting deposition holes on the basis of adiscriminating fracture
In Design premises long-term safety it is stated that: Deposition holes should be selected, as far as
is reasonably possible, so that they do not have a potential for shear displacements larger than thecanister can withstand. To achieve this, the EFPC criterion should be applied in selecting deposition
hole positions.
A report by /Cosgrove et al. 2006/ presents key properties and natural features of potentially discriminating structures, i.e. fractures and deformation zones. The term deformation zone is a collective term
and includes a large spectrum of structures ranging from discrete brittle fractures through fracture zones
to planar or sub-planar zones known as shear zones. The report concludes that it appears impossible todetermine the actual size of fractures and deformation zones. However, the parameters that most likely
reflect the size of fractures and deformation zones are identified. These parameters are:••••aperture,
shear displacement,
conductivity,
deformation zone thickness.

TR-10-18

51

The design premises stipulate that the EFPC criterion shall be applied in selecting deposition hole positions. The parameters and associated criteria for predicting and verifying a discriminating fracture or
deformation zone intersecting a deposition hole remain to finalise. The recognition of a fracture or adeformation zone in more than one borehole or tunnel is one of the most important techniques available for detecting large fractures and deformation zones. Fracture infilling (either minerals or water)
and wall rock alteration, both resulting from high fracture conductivity, are considered to be good
indicators of fracture size. Moreover, infilling will often provide the fracture with a clear geophysicalsignature that enables its extent to be determined using geophysical methods. Hence the final choiceof parameters and criteria are associated with the method used to identify such fractures or zones.
Monitoring and control programmes

SKB will develop a procedure for maximising the probability of detecting discriminating fractures anddeformation zones. Primarily this includes designing the investigative probe holes that precede tunnel
excavation. Geological mapping of tunnels and cores will provide detailed characterisation of the structures that intersect the tunnel. Before a deposition hole is excavated, a pilot hole is drilled. Core andborehole logging will provide information on the location and orientation of potentially discriminating
structures. Any structure, whose extrapolation would intersect an adjacent deposition hole or tunnel,
if the structure were sufficiently long, should be investigated. The reliability of the methods used formatching fractures and deformation zones between deposition holes and tunnels and or boreholes
remains to be assessed. These methods include cross-hole correlation (exploiting kinematic indicators)
and geophysical techniques such as borehole radar, which gives a good indication of the extent of thefracture into the rock around the hole. Hence application of the EFPC criterion requires results fromgeological characterisation, geophysical techniques and geological modelling. All deposition holes that
do not conform to the EFPC criterion shall be rejected and backfilled.

5.3.5 Bevel in the upper part of the deposition hole
To limit the height of the deposition tunnel and still make it possible to turn the canister with its radiation protection into an upright position, a bevel is constructed in the upper part of the deposition hole.
This upper part of the deposition hole is regarded as part of the deposition tunnel.
For the nominal tunnel height, the bevel must be 1.25 metres deep from the nominal tunnel floor and1.6 metres long measured from the periphery of the deposition hole, see Figure 5-2. The reference
method for construction of the bevel is wire sawing. The method has been demonstrated at the ÄspöHRL in connection with tests of the rail-bound deposition machine.

5.3.6 Preparation of deposition holes
Before installation of the buffer preparation of the deposition hole is carried out. The preparation ofdeposition holes comprises, see Buffer production line, Section 5.4.3:• removal of water and cleaning of the deposition hole,• inspection of inflow to the deposition hole (see Section 5.3.3),• inspection of potentially discriminating fractures intersecting the deposition hole (see Section 5.3.4),• installation and inspection of the bottom plate,• inspection to determine the dimensions of the deposition hole, i.e. radii and cross section as a function of depth, bottom inclination and total volume and location of the centre line (see Section 5.3.2).
The reference method for drilling deposition holes will not accomplish a flat bottom. In order toachieve a sufficiently flat bottom of the deposition hole a bottom plate is installed. The referencebottom plate consists of a low pH-cement concrete slab, and a lower and upper copper plate. At the
installation three bolts are fixed in the rock at the bottom of the deposition hole. The lower copper plateis placed on top of the bolts. The bolts are then used to adjust the copper plate into a horizontal position. After that the concrete is poured through a hole in the centre of the lower copper plate. Finally theupper copper plate is placed in the deposition hole. It is provided with fasten devices which are pressed
down into the fresh concrete through the hole in the lower plate. The upper plate is also provided witha border intended for auxiliary equipment for the installation of the buffer (see the Buffer production
report, Section 5.4.3). The bottom plate is illustrated in Figure 5-3 which also contains its main data.
A  detailed description of the bottom plate is given in /Wimelius and Pusch 2008/.

52

TR-10-18

Upper part ofdeposition hole

1.6 m

1.25 mNominal tunnel floor

Part where buffer
is installed

Nominal tunnel floor plane

Figure 5-2. The nominal dimensions of the bevel. This upper part of the deposition hole is regarded as partof the deposition tunnel.

The reference bottom plate is based on available knowledge and conventional technique, SKB foresees no difficulties in manufacturing and installing it in conformity to the specification. However,
SKB will study alternative ways to achieve a sufficiently flat bottom of the deposition hole.
After the bottom plate has been installed the geometry and position of the centre line of the deposition hole is measured in.

Lower copper plate resting on bolts fixed to the rock.
Thickness
20 mm
Diameter
1,710 mmHole diameter
450 mmNominal weight 382 kg

Concrete slab poured through the hole in the centreof the lower copper plate.
Thickness
150 mmNominal weight 650 kg
Concrete recipe See Table 5-1

Upper copper plate with fastening devices anda border intended for auxiliary equipment for
the installation of the buffer.
Thickness~10 mmDiameter
1,710 mmNominal weight 246 kg

Figure 5-3. The bottom plate in the deposition hole.

TR-10-18

53

Table 5-1. Concrete recipe for the foundation of the bottom plate /Pusch and Ramqvist 2007/.
Components

Amount (kg/m3 concrete)

Manufacturer

White cement

60

Aalborg Portland

Silica Fume

60

Elkem

Fine ground α-quartz M300

200

SibelcoFine ground cristobalite M6000

150

SibelcoSuperplasticizer Glenium® 51

4.375 (dry content)

Degussa

Granitic aggregates 0–4 mm

1,700

Jehanders grus

Water

244.27local

5.4

Reference methods associated with other
underground openings

The reference design for closure of main and transport tunnels, the ramp and shafts up to level–200 meter is to use clay blocks and pellets, i.e. the same reference design as for deposition tunnels.
The design premises imposed by the closure are given in Table 2-5 and Section 2.3.3. Prior to theclosure of the underground opening in question its conformity to the specified geometrical tolerances
and acceptable inflow shall be verified. At this stage the reference methods used in the constructionof deposition tunnels apply, although the design premises are less rigorous than those for deposition
tunnels. The closure design will be further developed and it is most probable that requirements on
the performance of reference methods used in the construction of the aforementioned undergroundopenings can be relaxed.

54

TR-10-18

6

Initial state of the underground openings

6.1

Introduction

The initial state of the underground openings refers to the properties of the underground openings atfinal installation of the buffer, backfill, closure or plugs. For the assessment of the long-term safety it
shall be confirmed that the underground openings at the initial state conform to the design premises
related to the functions in the final repository.
The presentation of the initial state comprises:•••

a summary of the design premises related to the functions the underground openings shall have inthe final repository together with the reference design for the Forsmark site and its conformity to
the design premises, Section 6.2,
an assessment of the geometry and other properties of importance for describing the initial stateof the engineered barriers; at this stage it only considers deposition holes and deposition tunnels,
Section 6.3,
an assessment of uncertainty and risk that the initial state of the underground openings does notconform to the design premises, Section 6.4.

6.2

Reference design at the Forsmark site

The reference design for a KBS-3 repository at the Forsmark site has been developed in accordancewith the design premises related to the functions of the underground openings in the final repository,
Table 2-1. The applied design methodology and the essential engineering tasks are described in/SKB 2007/.
The repository facility layout in the reference design is based on the current knowledge of the site
and adapted to the properties of the site as described in the current version of the SER /SKB 2009c/.
The reference design and its conformity to the design premises were presented in Chapter 4 and aresummarized in the following sections.

6.2.1 Repository depth and deposition areas
The repository depth shall be selected with respect to potential freezing, surface erosion and unintentional intrusion. Deposition areas and depth shall be selected with respect to hydrogeochemical
conditions and the possibility to find large enough volumes to host the required number of deposition
holes, Table 2-1. The determination of repository depth and the basis for the utilisation of depositionareas is presented in sections 4.1 and 4.2 and summarized below.
The repository depth, defined as the depth from the 0-level to the roof of the highest located deposition tunnel, shall according to SER be located at elevations ranging between –450 m and –500 m.
The current reference design has been established with a minimum depth at elevation –457 metres
and a maximum depth at elevation –470 metres. Thereby the risk for encountering water bearing
fractures without significantly increasing the risk for spalling is reduced.
The layout and the utilisation of deposition areas are significantly influenced by the design premises
for deposition holes, Table 2-1. The primary design constraints are: (1) deformations zones requiringa respect distance and (2) thermal properties of the rock mass as well as the approach used in thethermal dimensioning.
In the reference design potential deposition hole positions are not located within 100 m perpendiculardistance from the boundaries of deterministic deformation zones that have a 3 km trace length orequivalent size.
The reference design layout is based on a fixed distance between deposition tunnels. The specified
minimum centre-to-centre spacing is 40 m. Further, a minimum distance between deposition holes
TR-10-1855

of 6.0 m was a premise for the design. The minimum distance between deposition holes shall be
determined with respect to the maximum allowed temperature in the buffer, Table 2-1. The thermal
conductivity of the different rock domains was the basis for determining the distance between deposition holes. A conservative approach was employed and the minimum centre-to-centre spacing for thedeposition holes is 6.0 m in RFM029 and 6.8 m in RFM045.
The justification of that the rock volumes selected for deposition areas in the reference design havefavourable chemical conditions for deposition holes is found in /SKB 2009c/. The reference design
does not verify favourable chemical conditions in individual deposition holes.

6.2.2 Deposition tunnels
The deposition tunnels shall be constructed so that the excavation-induced damage and the resulting
connected transmissivity is limited (EDZ). Further, continuous grouting holes outside the tunnel
perimeter and continuous grouting is not allowed, and only low pH cement may be used, Table 2-1.
The orientations of the deposition tunnels for the reference design shall be aligned within ±30 degreesof the trend of the maximum horizontal stress, Section 4.4. In the reference design the deposition
tunnels are aligned between and 0 and 30 degree relative to the direction of the major horizontal stress.
Assessments of stress concentrations in the rock mass surrounding the deposition tunnels indicate thatthey are below the current estimate of the spalling strength that was used for the reference design.
The need for grouting and rock reinforcement and the resulting amounts of engineered materials forthe reference design is presented in Section 4.6. Only low pH cement is used in the reference design.
The grouting methodology comprises three different cement-based grout mixes with a low pH. All
cement mixes used in shotcrete support and for embedding various rock support elements are basedon low pH cement.

6.2.3 Deposition holes
With respect to the functions in the final repository the deposition holes shall be placed so that thepotential for shear displacements, water inflow and connected transmissivity are limited, Table 2-1.
The design premises for deposition holes that significantly influence the loss of potential deposition
positions are; (1) minor deformation zones or discriminating structures or frequency of water-bearing
fractures and (2) direction and magnitude of the major horizontal stress.
The location of structures with potential for shear displacements, i.e. discriminating fractures anddeformation zones, cannot be determined deterministically at this stage, Section 4.2.2. While itis very likely that some deposition positions will be rejected due to discriminating factures, it isextremely unlikely that this will impose a risk on the design premise to accomadate about 6,000
canisters /SKB 2009b/.
Very few additional deposition holes will be lost due to high inflows as most of these positions arelikely to be screened out by the criterion for discriminating fractures, Section 4.2.2.
The major horizontal stress magnitude as well as a favourable orientation of deposition tunnels in thegeneral direction of the major horizontal stress is of importance to reduce the occurrence of spalling(EDZ) in deposition holes. While there is high confidence in the design methodology utilised toassess the spalling potential for the reference design, there are uncertainty relative to the in situ stressconditions and the rock properties. This restricts the capability to model the extent of spalling and theassociated change in transmissivity at this stage and additional investigations will be needed at therepository level to confirm the design assumptions.
Elevated stress magnitudes relative to the current reference design may result in realignment of deposition tunnels in the general direction of maximum horizontal stress. For the “unlikely maximum”
stress model the tunnels must be aligned with the maximum horizontal stress to reduce the risk ofspalling. The number of deposition holes in the reference design that may have to be rejected due tospalling is presented in Figure 4-3. It was assessed for the “unlikely maximum” stress model thataligning deposition tunnels with the maximum horizontal stress results in that approximately 100–200

56

TR-10-18

deposition holes (out of 6,000) would sustain a spalling depth that exceeds the acceptable variation in
deposition hole radius imposed by the buffer (also see Buffer production report, Section 6.1.4).
To summarise, the repository layout in the reference design has a gross capacity of 7,818 deposition
hole positions which is sufficient for hosting the required 6,000 canisters provided that less than 23%(1,818) of the potential deposition positions are rejected.

6.3

Geometry and properties of importance for the initial state of
the engineered barriers

The expected geometry and other properties of importance for the reliable installation of the engineered
barriers according to specification and the extent of the EDZ will mainly depend on the performanceof the methods for excavation (reference methods). The results that were used when determining theinitial state of the engineered barriers are based on experiences and results presented in Chapter 5 andare summarized in the following sections.

6.3.1 Buffer and deposition holes
The buffer imposes design premises for the straightness, radius and maximum area of the deposition
holes, Table 2-2 and Figure 2-1. In addition, the potential for occurrence of EDZ due to the excavation
method must also be considered.
The results from drilling the deposition holes included in the Prototype Repository showed that thedrilling accuracy is acceptable and that the dimensions of the deposition holes conforms to the current
design premises, Section 5.3.2. Applying this experience to deposition holes excavated with a reamer
head having the nominal diameter (1,750 mm), the most likely range of cross-sectional mean diameters
would be found between 1,750 to 1,765 mm. However, for any occurrence of rock fall out or looseningof rock due to spalling it is required to improve the accuracy in drilling in direct proportion to thespalling depth (also see Buffer production report, Section 6.1.4).
The full-face down hole drilling method, which is the reference method, creates very little damage
to the surrounding rock walls, Section 5.3.1. A reasonable value for the hydraulic conductivity of the
EDZ, which is limited to a few centimetres in extent, is in the order of 10–10 m/s /Bäckblom 2008/.
This magnitude is valid in rock conditions where spalling has not occurred.
The impact from occurrences of spalling on the installed buffer density and the possibility to adapt
the installation of the buffer to the actual deposition hole geometry is discussed in the Buffer
production report, Section 6.2.2.

6.3.2 Backfill and deposition tunnels
The backfill imposes design premises for the volume, maximum cross section, evenness of thetunnel floor and inflow to deposition tunnels, Table 2-3 and Figure 2-2. For the deposition tunnels
EDZ created by the excavation method should be limited with respect to its contribution to theconnected effective transmissivity.
The results from applying smooth-blasting techniques at the Äspö Hard Rock Laboratory showedthat the reference method for excavation of deposition tunnels conform to the current design premises,
Section 5.2.
Applying the experience from Äspö HRL to deposition tunnels in the reference design, the average
excavated volume per round is assessed to be approximately 18% larger than the nominal volume.
The rock surfaces in tunnels excavated by drill and blast will be rough and it cannot be excluded that
small volumes of rock will protrude inside the nominal cross-section. However, this is easy to correct.
Moreover, the smooth-blasting techniques resulted in blast-induced fractures that are dominantly
radial in direction. Such fractures are not continuous along the axial direction of the tunnel over any
significant distance.

TR-10-18

57

SKB will develop a reference method that can provide a tunnel floor contour that conforms to thedesign premises imposed by the backfill, Section 5.2.3. A feasibility study of potential methods isongoing in which smooth blasting techniques and wire sawing techniques, or combinations thereof,
are assessed.
The open flowing fracture frequency at the repository level indicates a rock mass with very few open
fractures and consequently that the inflows to deposition tunnels may be very low, Section 4.6.2.
Cumulative density functions of transmissivity values in 20 m long sections, deformation zones
excluded, indicates that on average less than 2% of the 20 m long sections will require grouting
measures /SKB 2009c/.

6.4

Uncertainty and risk relative to the initial state

6.4.1 General basis
There are three general categories of uncertainties which may contribute to the risk that the initialstate of the underground openings in the repository facility does not conform to the design premises.
These uncertainties are related to:
1. site conditions (geohazards),
2. adequacy of design methodologies,
3. performance of reference methods.
The objective here is to assess the risk of nonconformity to the functions, geometry and other propertiesof importance for the final repository. The risk of rejecting underground openings for which the initialstate conforms to the design premises is not analysed.
Uncertainties in the reference design and in the reference methods were discussed in Chapter 4 andChapter 5, respectively.
The occurrences of geohazards were evaluated with qualitative risk analyses in /SKB 2009b/ inwhich potential consequences for the repository facility were assessed in terms of loss of deposition
positions. The confidence in the design methodologies that were used to establish the reference design
was also judged in /SKB 2009b/. The confidence in the adequacy of the applied design methodologies
is acceptable or high, and its contribution to risk is considered to be negligible relative to the othertwo general categories of uncertainties, geohazards and hazards associated with reference methods.
The current risk assessment has emphasis on deposition tunnels and deposition holes. Only unwanted
events (hazards) that would have widespread impact on the conformity of the underground openings
to the design premises were considered. Local occurrences of unwanted events, e.g. human errors,
were not evaluated. The reason is that localised events were not expected to alter the overall assessment of the initial state. Such events, in most cases, were considered possible to mitigate by means ofquality control and assurance procedures and contingency measures and are therefore negligible forthe initial state.
The current risk assessment is qualitative. Quantitative analyses using probability functions will
be appropriate at a later stage when descriptions of uncertainties and the underlying data which are
input to the assessment are well defined.

6.4.2 Geohazards, design methodologies and reference methods
The uncertainties in the site geological conditions, geohazards, and the consequences of these geohazards with respect to design are summarised in /SKB 2009b/. Table 6-1 provides a summary of thegeohazards that were evaluated for the reference design and the general locations in the repository
where the geohazard would be monitored.
In order to evaluate the risk for nonconformity to the design premises at the initial state, the firststep is to assess the likelihood of occurrence of identified geohazards and hazards associated withreference methods.

58

TR-10-18

Table 6-1. Catalogue of geohazards evaluated for the reference resign as well as the monitoring
locations associated with the hazards. The table also includes the identifiers for the assessed
hazards, a letter followed by an integer number, G1, H1, etc. (adapted from /SKB 2009b, Table 8-3/).
Geohazard: Geology

Monitoring location(G1) Distribution of rock types

All excavations(G2) Geological boundaries

All excavations(G3) Frequency of large fractures

Deposition tunnels and deposition holes(G4) New deformation zones between 1km and 3km trace
length or equivalent size

All excavations(G5) New deformation zones requiring respect distanceAll excavations(G6) Thickness of minor deformation zones (MDZ<1km)

All excavations

Geohazard: Hydrogeology

Monitoring location(H3) Frequency of discrete flowing fractures, with flows
unsuitable for deposition holes or deposition tunnels

Deposition tunnels and deposition holes

Geohazard: Rock mechanics/in situ stress

Monitoring location(R1) Properties of the major and minor deformation zones

All excavations(R2) Orientation of major horizontal stress

Skip shaft & ramp
Deposition tunnels(R3) Horizontal stress magnitudes

Skip shaft & ramp
Deposition tunnels

Geohazard: Thermal

Monitoring location(T1) Geometrical distribution of thermal rock domains

Deposition tunnels and deposition holes(T2) Rock containing mafic (Amphibolite) dykes(low T properties)

Deposition tunnels and deposition holes

The geohazards were grouped according to geology, hydrogeology, rock mechanics and in situ stress,
and thermal properties. The likelihood of occurrence for geohazards was described using four descriptors, extremely unlikely, unlikely, likely and very likely. The descriptor aims at assessing the risk thatthe description of the site provided in the SDM /SKB 2008/ is incorrect. The descriptor extremely
unlikely in the context of geohazards implies that there is simply no evidence from the site investigations to support the occurrence of the geohazard within the rock volume for the repository facility,
while the descriptor very likely implies that the geohazard is expected to occur.
The likelihood of occurrence for hazards associated with the performance of reference methods
were evaluated using the same four likelihood descriptors, extremely unlikely, unlikely, likely
and very likely. The descriptor aims at assessing the risk for implications on the initial state of theunderground openings located in deposition areas. The descriptor extremely unlikely implies that
there is documented evidence that the reference method is reliable relative to the design premises,
i.e. proven in operation or demonstrated functional, while the descriptor very likely implies that thehazard associated with the reference method is expected to occur, i.e. unacceptable performance.
Having identified the geohazards and the hazards associated with reference methods as well as theirlikelihood of occurrence, it remains to assess the risk of nonconformity of the underground openings
to the design premises at the initial state. The initial state shall be evaluated by means of monitoring
programmes and by implementing control programmes including control and quality assurance ofthe construction works, see Chapter 3. The reliability of the results from such programmes depends
on the underlying technology, i.e. means and methods for investigation, characterisation, modellingand monitoring. The reliability were categorised based on the demonstrated performance, see
Chapter 5. The qualitative confidence classes are defined in Table 6-2.

TR-10-18

59

Table 6-2. Qualitative confidence classes are used for categorising the status of monitoring andcontrol programmes which are employed to evaluate the initial state.
Confidence category

Status of monitoring and control programmes

High

Operational and/or successfully demonstrated

Acceptable

Conceptual with proven technology and/or
demonstrated feasible

Low

Conceptual with new technology or unprovenapplication

Hence the risk assessment of the initial state relative to nonconformity to the design premises is formed by
the combination of two basic components; (1) likelihood of hazards relative to the geological site conditions (geohazards) or of hazards associated with the reference methods and (2) confidence in the resultsfrom the monitoring and control programmes that shall be employed to evaluate the initial state. Only one
component is considered at a time, the other components are assumed to have the expected function.

6.4.3 Risk matrix
The results of the likelihood-confidence analyses are presented in a risk matrix, see Figure 6-1. The risk
matrix provides means of ranking the hazards, visualize the results for each analysed design premise
and identify unwanted events as a basis for deciding mitigation measures. For example, pointing out
technical issues that need to be resolved in further developing the reference methods. For the risk
matrix in Figure 6-1 only two categories of risk are identified:
1. Risk class N/A – the risks is considered negligible and/or acceptable, and2. Risk class S/U – the risks is considered significant and/or unacceptable.
Risk category N/A reflects that the risk of accepting an underground opening with a non-conforming
initial state is negligible or can be accepted because mitigation measures can be taken within thecurrent reference design, or will be handled in the planned development of reference methods or in
the planned development of the technology in the monitoring and control programmes.
Risk category S/U reflects that the risk of an initial state that does not conform to the design premises is imminent. This indicates that major changes may have to be imposed on the reference designor that the risk is not handled in the planned development of reference methods or in the planneddevelopment of the monitoring and control programmes. Risk category S/U need to be evaluated on
an individual basis but indicates that:
additional site information should be collected as soon as practical to resolve the uncertainty withthe geohazard,• the performance of the reference method is uncertain and that ongoing development need toconsider improvements to the technology platform on which the reference method is based,• the performance of the underlying technology in the monitoring and control programmes is notreliable and that ongoing development need to be accelerated or revised.

Likelihood of­occurrence for­identified hazards•

Very likely

N/A

S/U

S/U

Likely

N/A

N/A

S/U

Unlikely

N/A

N/A

S/U

Extremely
Unlikely

N/A

N/A

N/A

High

Acceptable

Low

Confidence in results from monitoring and control programmes

Figure 6-1. Illustration of the risk matrix used for presenting the results of evaluating the likelihoodconfidence analyses for the initial state.

60

TR-10-18

6.4.4

Qualitative risk assessment of the initial state for repository depth anddeposition areas
The relevant design premises for repository depth and deposition areas presented in Table 2-1 arerepeated below for easy reference. The reference design and initial state is summarised in Section 6.2.1.
With respect to potential freezing of buffer and backfill, surface erosion and inadvertent human
intrusion the depth should be considerable. Analyses in the SR-Can assessments corroborate that
this is achieved by prescribing the minimum depth to be as specified for a KBS-3 repository i.e. atleast 400 m.
• Reducing conditions: salinity – TDS limited; ionic strength – [M2+] > 1 mM; concentrations of K,
HS− Fe; limited; pH; pH < 11; avoid chloride corrosion – pH > 4 or [Cl−] < 3M.
• The repository volumes and depth need to be selected where it is possible to find large volumesof rock fulfilling the specific requirements on deposition holes.
•

The content in the last bullet point implies that the specific design premises for deposition holes shallbe considered here. There are four primary design constraints concerning deposition holes that significantly influence the repository layout and the utilisation of deposition areas. (1) deformations zones
requiring a respect distance, (2) minor deformation zones or discriminating structures or frequency ofwater-bearing fractures, (3) thermal properties of the rock mass and the approach used in the thermal
dimensioning and (4) direction and magnitude of the major horizontal stress.
The uncertainty imposed on the initial state with respect to repository depth and deposition areas areassociated with the geological site conditions and hence the potential impact of geohazards. Table 6-3
provides a summary of the likelihood of occurrence for the geohazards, the confidence classes formonitoring programmes and a short discussion about their current reliability. The results of thelikelihood-confidence analysis are visualized in the risk matrix shown in Figure 6-2. Considering
the occurrence and confidence in the reference methods none of the identified geohazards have arisk level which indicates that the repository depth and deposition areas at the initial state would notconform to the design premises.
For the geohazards R2, R3, R4 (Rock mechanics/in situ stress – orientation and magnitude of maximum horizontal stress) and T1 (Thermal – distribution of thermal rock domains), it was found that
there is acceptable confidence in the results from monitoring programmes which are intended fortheir identification and characterisation. This indicates that the current status of the field methods canbe considered as conceptual and that further development would be needed as well as demonstrationof their reliability. The objective for further development would be to verify the assumptions in thereference design layout, i.e. the “most likely” stress model and that the orientation of the maximum
horizontal stress does not vary more than ±15 degrees and that the geometrical distribution ofthermal rock domains does not deviate from the design values.

TR-10-18

61

Table 6-3. Qualitative risk assessment showing likelihood of occurrence for the identified
hazards and the confidence in detecting that the initial state of underground openings does notconform to the design premises listed in Section 6.4.4. 2
Geohazard2

Likelihood of Confidence
occurrence
in results

Current reliability(G1) Distribution of rock types deviatesfrom the design value

UnlikelyHigh(G2) Geological boundaries deviatesfrom those used in the design

LikelyHigh(G3) Frequency of large fractures
exceeds the values predicted by thegeological DFN Model

Extremely
UnlikelyHigh

These geohazards can be identified andcharacterised with methods and techniquesthat were implemented during the site investigations. These methods and techniques
are judged to produce reliable results,
their performance is demonstrated and thedegree of new technology involved in further
development is not foreseen to introduce
unforeseen uncertainties.

(G4) New deformation zones between
1 km and 3 km long trace length orequivalent size

UnlikelyHigh(G5) New deformation zones requiring
respect distance

Extremely
UnlikelyHigh(G6) Thickness of minor deformation zones (MDZ<1km) exceeds theestimated values in SDM-SiteUnlikelyHigh(H3) Frequency of discrete flowing frac- Extremelytures, with flows unsuitable for deposition Unlikely
holes or deposition tunnels, below 400 m
in FFM01 exceeds the hydrogeological
DFN prediction used in the designHigh(R1) Properties of the major and minor
deformation zones deviates from thedesign value

UnlikelyHigh(R2) Orientation of maximum horizontal stress (σhmax) varies more than
±15 degrees

Unlikely

Acceptable(R3) Horizontal stress magnitudes
exceed “most-likely” model but not the“Unlikely maximum model”

Unlikely

Acceptable(R4) Horizontal stress magnitudes
exceed the “Unlikely maximum” model

Extremely
Unlikely

Acceptable(T1) Geometrical distribution of thermalrock domains deviates from the designvalue

Unlikely

Acceptable

Stress measurements can be carried out inboreholes and the orientation of the stressfield was evaluated using indicators suchas observations of breakouts in boreholes/Martin 2007/. These methods are proventechnology and judged to produce reliable
results, however some degree of newtechnology and innovation are involved indeveloping suitable field methods.
The distribution of thermal rock domains canbe identified and characterised with methods
based on proven technology. The thermal
properties were determined in laboratory
scale during the site investigations. The
methods used are judged to produce reliable
results however, some degree of newtechnology and innovation are involved indeveloping suitable field methods.

2
Abbreviations used in Table 6-3 and Figure 6-2: (G1), (R1) etc. are identifiers, where (G) is short for Geology
model, (H) Hydrogeological model, (R) Rock Mechanics/in situ Stress model and (T) Thermal model /SKB 2009b/.

62

TR-10-18

Likelihood

Very likely
LikelyG2

Unlikely

G1, G4, G6, R1

R2, R3, T1

Extremely Unlikely

G3, G5, H3

R4

High

Acceptable

Low

Confidence in results from monitoring
and control programmes

Figure 6-2. Risk matrix showing likelihood of occurrence for the identified hazards and the confidence indetecting that the initial state of underground openings does not conform to the design premises listed in
Section 6.4.4.

6.4.5 Qualitative risk assessment of the initial state for deposition tunnels
The relevant design premises presented in Section 2.3 are repeated below for easy reference. The
reference design and expected initial state is summarised in Sections 6.2.2, and 6.3.2. The designpremises associated with functions in the final repository are:• Only low pH materials (pH<11),
No continuous shotcrete,
Continuous grouting boreholes, outside tunnel perimeter should be avoided.
• Excavation induced damage should be limited and not result in a connected effective transmissivity, along a significant part (i.e. at least 20–30 m) of the disposal tunnel and averaged across thetunnel floor, higher than 10–8 m2/s. Due to the preliminary nature of this criterion, its adequacy
needs to be verified in SR-Site.
The design premises imposed by the backfill are:
• Based on current experiences the maximum distributed inflow into the deposition tunnel is set tobe less than or equal to 1.7 l/min 100 m (based on 5 l/min in a 300 m long deposition tunnel) andthe maximum point inflow less than or equal to 0.1 l/min.
• For each blast round the total volume between the rock wall contour and the nominal contour ofthe deposition tunnel shall be less than 30% of the nominal tunnel volume, see Figure 2-2.
• The maximum cross section shall be less than 35% larger than the nominal cross section, see
Figure 2-2.
• To achieve a dependable backfill installation the tunnel floor must be even enough for the backfill
installation equipment to drive on it.
• Underbreak is not allowed.
• Limited areas may be covered with construction materials. The areas must not extend over thefull tunnel width.
The uncertainty imposed on the initial state with respect to deposition tunnels is associated with thepotential impact of hazards related to the performance of the reference methods employed in theconstruction of the repository facility. Table 6-4 provides a summary of the likelihood of occurrence
for the hazards, the confidence classes for monitoring and control programmes and a short discussion
about their current reliability. The results of the likelihood-confidence analysis are visualized in therisk matrix shown in Figure 6-3. None of the identified hazards related to the reference methods havea risk level which indicates that the initial state would not conform to the design premises.
It was found that there is acceptable confidence in the results from the monitoring and control
programmes which are intended for managing the hazard RM5 (need for characterisation or acceptance criteria for EDZ). This indicates that the current status of the field method can be considered asconceptual and that further development would be needed as well as demonstration of the reliability,
see Section 5.2.1.
TR-10-18

63

Table 6-4. Qualitative risk assessment showing likelihood of occurrence for the identified hazards
and the confidence in detecting that the initial state of deposition tunnels does not conform to
the design premises listed in Section 6.4.5. 3
Hazard3

Likelihood of
occurrence

Confidence inresults

Current reliability(RM1) The grouting methodology Very Likely
need to be further developed relative to the current performanceand the specified inflows

High

There are uncertainties whether the performanceof the grouting methodology is reliable relative tothe very low inflows specified for the initial state. It
is relatively straightforward to monitor the inflow todeposition tunnels and to evaluate the initial state
as discussed in Section 5.2.4.

(RM2) The drilling and smooth
blasting techniques need to befurther developed relative to thecurrent performance and thespecified connected effective
transmissivity from EDZ

High

The EDZ can be controlled by applying control
programmes for drilling, charging and ignition.
No specific method or combination of methods
can yet be recommended for quantifying the connected effective transmissivity. The procedures
and results from inspections, geological characterisation, geophysical techniques and geologicalmodelling will be applied to verify that the damage
in deposition tunnels conforms to the designpremises. Although the basis is proven technology
a certain degree of new technology and innovation
is likely to be involved to develop the monitoring
and control programmes, Section 5.2.1.

Unlikely(RM5) Practical characterisation
Likelyor acceptance criteria relative to
EDZ need to be further developed

Acceptable(RM3) The drilling and smooth
Extremely
blasting techniques need to be
Unlikely
further developed relative to thecurrent performance and thespecified geometrical tolerances
for maximum cross-section, excavated volume and underbreakHigh

The geometrical tolerances can be controlled byapplying control programmes for drilling, charging
and ignition.
There are suitable methods and instruments forinspecting the geometry of deposition tunnels,
e.g. laser scanning and geodetic methods. Thesemethods and techniques are proven, their performance is demonstrated and the degree of newtechnology involved in further development is notforeseen to introduce unforeseen uncertainties,
Section 5.2.2.

(RM4) The excavation techniquefor providing a sufficiently smoothtunnel floor contour need to befurther developed relative to thecurrent performance and thespecified geometrical tolerances

High

There are uncertainties relative to the performance of the current conceptual reference
method.
There are suitable methods and instruments forinspecting the geometry of the deposition tunnel
floor, e.g. laser scanning and geodetic methods.
These methods and techniques are proven, theirperformance is demonstrated and the degreeof new technology involved in further development is not foreseen to introduce unforeseen
uncertainties, Section 5.2.2.

3

Very Likely

Abbreviations used in Table 6-4 and Figure 6-3: (RM) is short for Reference methods, see Chapter 5.

64

TR-10-18

Very likely

RM1, RM4
RM5

Likelihood

LikelyUnlikely
Extremely Unlikely

RM2
RM3
High

Acceptable

Low

Confidence in results from monitoring and control
programmes

Figure 6-3. Risk matrix showing likelihood of occurrence for the identified hazards and confidence indetecting that the initial state of deposition tunnels does not conform to the design premises listed in
Section 6.4.5.

6.4.6 Qualitative risk assessment of the initial state for deposition holes
The relevant design premises presented in Section 2.3 are repeated below for easy reference. The
reference design and expected initial state of the deposition holes is summarized in Section 6.2.3 and6.3.1. The design premises associated with functions in the final repository are:
The buffer geometry (e.g. void spaces), water content and distances between deposition holes
should be selected such that temperature in the buffer is <100°C.
• Deposition holes should, as far as reasonably possible, be selected such that they do not havepotential for shear larger than the canister can withstand. To achieve this, the EFPC criterion
should be applied in selecting deposition hole positions.
• Fractures intersecting the deposition holes should have sufficiently low connected transmissivity(specific value cannot be given at this point). This condition is assumed to be fulfilled if theconditions regarding inflow to deposition holes are fulfilled.
• The total volume of water flowing into a deposition hole, for the time between when the buffer is
exposed to inflowing water and saturation, should be limited to ensure that no more than 100 kgof the initially deposited buffer material is lost due to piping/erosion. This implies, according to
the present knowledge, that this total volume of water flowing into an accepted deposition holemust be less than 150 m3.
• Before canister emplacement, the connected effective transmissivity integrated along the fulllength of the deposition hole wall and as averaged around the hole, must be less than 10–10 m2/s•

The design premises imposed by the buffer are:
•
•
•
•
•
•

The diameter and height of the deposition hole shall allow sufficient room to accommodate thecanister and buffer; the resulting nominal diameter is 1.75 m and the minimum depth is 6.68 m.
The inclination over the part of the cross section where the bottom buffer block is placed shall beless than 1/1,750.
In the part of the deposition hole where buffer is going to be deposited the diameter shall be atleast 1.745 m. The nominal diameter is 1.75 m.
From the buffer block on top of the canister to the bottom of the deposition hole the radius from a
vertical line in the centre of the buffer rings shall be at least 840 mm.
From the buffer block on top of the canister to the bottom of the deposition hole the radius from a
vertical line in the centre of the buffer rings must not exceed 925 mm.
In the part of the deposition hole where buffer is going to be deposited the maximum area in eachhorizontal cross section must not exceed the nominal cross section by more than 7.0%.

The uncertainties regarding the initial state of the deposition holes are related to geohazards as well as
to hazards related to the performance of the reference methods. Table 6-5 provides a summary of the

TR-10-18

65

likelihood of occurrence for the hazards, the confidence classes for investigation and monitoring andcontrol programmes and a short discussion about their current reliability. The results of the likelihoodconfidence analysis are visualized in the risk matrix shown in Figure 6-4. Considering the occurrence
and confidence in the reference methods none of the identified geohazards have a risk level whichindicates that the deposition holes at the initial state would not conform to the design premises.
It was found that there is acceptable confidence in the results from investigation and monitoring andcontrol programmes which are intended for managing the hazards associated with shear movements(RM7), connected effective transmissivity (RM5, RM6) and geometrical tolerances (RM8). This
indicates that the current status of the field methods can be considered as conceptual and that further
development would be needed as well as demonstration of their reliability.
Table 6-5. Qualitative risk assessment showing likelihood of occurrence for the identified hazards
and the confidence in detecting that the initial state of deposition holes does not conform to thedesign premises listed in Section 6.4.6. 4
Hazard4

Likelihood of Confidence Current reliability
occurrence
in results(T2) Rock containing
mafic (Amphibolite)
dykes (low thermal
properties) occurs more
frequently causing thethermal conductivity
distribution in the upscaled model to be lessthan the design value.

UnlikelyHigh

The hazard is associated with exclusion of potential deposition
positions as well as verifying the distance between deposition
holes. The effective way of ensuring that the thermal propertiesare determined correctly would be to combine geological characterisation with measurement techniques. These dark rocktypes are discrete in nature and can be identified with techniques that were implemented during the site investigations.
The instruments and measurement techniques are judged to
produce reliable results, their performance is demonstrated
and the degree of new technology involved in the development
programme is not foreseen to introduce new uncertainties. In
addition, it is also possible to verify the reference design byin situ tests at repository depth.

(RM7) The current meth- Likely
odology for accepting
or rejecting deposition
holes on the basis ofdiscriminating fracturesneed to be further
developed relative tothe current performanceand the specified EFPC
criterion.

Acceptable

No specific method or combination of methods can yet berecommended for quantifying the size of fractures or deformation
zones. Results from investigations, geological characterisation,
geophysical techniques and geological modelling will be required
to apply the EFPC criterion. The tool box is considered to beconceptual and although the basis is proven technology a certain
degree of new technology and innovation is likely to be involved
to develop the monitoring programme, see Section 5.3.4.

(H3) Frequency of discrete flowing fractures,with flows unsuitablefor deposition holes
or deposition tunnels,
below 400 m in FFM01
exceeds the hydrogeological DFN predictionused in the design.

Extremely
UnlikelyHigh

It is foreseen that most of the planned positions for deposition
holes having a potential for unacceptable inflows are likely
to be screened out by the EFPC criterion. Combining resultsfrom hydrogeological characterisation and geological modelling in different scales will provide additional confidence inthe selected deposition hole positions. Measuring inflow todeposition holes is relatively straightforward and to establish
such a monitoring programme is not foreseen to introduce new
uncertainties, Section 5.3.3.

(RM8) The current fullface down-hole drilling
technology and themethods to verify theperformance need to
be further developed
relative to the specified
geometrical tolerances.

Unikely

Acceptable

The geometrical tolerances can be controlled by applying acontrol programme for the drilling operations. There are suitable methods and instruments for inspecting the dimensionsof deposition holes, e.g. laser scanning and geodetic methods.
However the current methods are considered to be conceptualand although the basis is proven technology a certain degreeof new technology and innovation is likely to be involved todevelop the control programme, Section 5.3.2.

Abbreviations used in Table 6-5 and 6-4: (H3), (RM7) etc. are identifiers, where (H) is short for Hydrogeologicalmodel and (T) Thermal model /SKB 2009b/. (RM) is short for Reference methods, see Chapter 5.

4

66

TR-10-18

Hazard4

Likelihood of Confidence Current reliability
occurrence
in results(RM6) The current fullface down-hole drilling
technology and themethods to verify theperformance need to
be further developed
relative to the specified
connected effective
transmissivity.

Extremely
Unlikely

Acceptable(RM5) Practical characterisation or acceptancecriteria relative to EDZ
need to be further
developed.

LikelyAcceptable

No specific method or combination of methods can yet berecommended for quantifying the connected effective transmissivity. It is assumed that the deposition holes conform to
the design premises for connected effective transmissivity ifthey conform to the design premise for acceptable inflow.
Results from inspections, geological characterisation, geophysical techniques and geological modelling will be applied
to verify that the connected effective transmissivity in deposition holes conforms to the design premises. These methods
are considered to be conceptual and although the bases isproven technology a certain degree of new technology andinnovation is likely to be involved to develop the monitoring
programme, Section 5.3.1.

Very likely

Likelihood

LikelyRM5, RM7

Unlikely

T2

RM8

Extremely Unlikely

H3

RM6

High

Acceptable

Low

Confidence in results from monitoring and control programmes

Figure 6-4. Risk matrix showing likelihood of occurrence for the identified hazards and confidence
for detecting that the initial state of deposition holes does not conform to the design premises listed in
Section 6.4.6.

TR-10-18

67

References
SKB’s (Svensk Kärnbränslehantering AB) publications can be found at www.skb.se/publications.

Backfill production report, SKB 2010. Design, production and initial state of the backfill and plugin deposition tunnels. SKB TR-10-16, Svensk Kärnbränslehantering AB.
Buffer production report, SKB 2010. Design, production and initial state of the buffer.
SKB TR-10-15, Svensk Kärnbränslehantering AB.
Closure production report, SKB 2010. Design, production and initial state of the closure.
SKB TR-10-17, Svensk Kärnbränslehantering AB.
Design premises long-term safety, SKB 2009. Design premises for a KBS-3V repository based on
results from the safety assessment SR-Can and some subsequent analyses. SKB TR-09-22, Svensk
Kärnbränslehantering AB
Repository production report, SKB 2010. Design and production of the KBS-3 repository.
SKB TR-10-12, Svensk Kärnbränslehantering AB.
Andersson C, Johansson Å, 2002. Boring of full scale deposition holes at the Äspö Hard RockLaboratory. Operational experiences including boring performance and a work time analysis.
SKB TR-02-26, Svensk Kärnbränslehantering AB.
Bäckblom G, 2008. Excavation damage and disturbance in crystalline rock – results from­experiments and analyses. SKB TR-08-08, Svensk Kärnbränslehantering AB.
Cosgrove J, Stanfors R, Röshoff K, 2006. Geological characteristics of deformation zones and astrategy for their detection in a repository. SKB R-06-39, Svensk Kärnbränslehantering AB.
EN 1997-1:2004. Eurocode 7. Geotechnical design – Part 1: General rules. Brussels: European
Committee for Standardization.
Ericsson L O, Brinkhoff P, Gustafson G, Kvartsberg S, 2009. Hydraulic features of the
Excavation Disturbed Zone – Laboratory investigations of samples taken from the Q- and S-tunnels
at Äspö HRL. SKB R-09-45, Svensk Kärnbränslehantering AB.
Fransson Å, 2008. Grouting design based on characterization of the fractured rock. Presentation anddemonstration of a methodology. SKB R-08-127, Svensk Kärnbränslehantering AB.
Funehag J, 2008. Injekteringen av TASS-tunneln. Delresultat t o m september 2008. SKB R-08-123,
Svensk Kärnbränslehantering AB (in Swedish).
Hökmark H, Sundberg J, Lönnqvist M, Hellström G, Kristensson O, 2009. Strategy forthermal dimensioning of the final repository for spent nuclear fuel. SKB R-09-04, Svensk
Kärnbränslehantering AB.
Jonsson M, Bäckström A, Feng Q, Berglund J, Johansson M, Mas Ivars D, Olsson M, 2009. ÄspöHard Rock Laboratory. Studies of factors that affect and controls the Excavation Damaged/Disturbed
Zone. SKB R-09-17, Svensk Kärnbränslehantering AB.
Lindgren M, Pers K, Södergren Riggare S, 2009. Främmande material i slutförvaret Forsmark.
Inventering för SR-Site. SKB P-09-07, Svensk Kärnbränslehantering AB (in Swedish).
Malmtorp J, Andersson C, Karlzén R, 2009. Berguttag i TASS-tunneln. Delresultat t o m september 2008. SKB R-08-122, Svensk Kärnbränslehantering AB (in Swedish).
Martin C D, 2005. Preliminary assessment of potential underground stability (wedge and spalling)at Forsmark, Simpevarp and Laxemar sites. SKB R-05-71, Svensk Kärnbränslehantering AB.
Martin C D, 2007. Quantifying in situ stress magnitudes and orientations for Forsmark. Forsmark
stage 2.2. SKB R-07-26, Svensk Kärnbränslehantering AB.
Munier R, 2006. Using observations in deposition tunnels to avoid intersections with critical
fractures in deposition holes. SKB R-06-54, Svensk Kärnbränslehantering AB.

TR-10-18

69

Munier R, 2007. Demonstrating the efficiency of the EFPC criterion by means of sensitivity
analyses. SKB R-06-115, Svensk Kärnbränslehantering AB.
Munier R, 2010. Full perimeter intersection criteria. Definitions and implementations in SR-Site .
SKB TR-10-21, Svensk Kärnbränslehantering AB.
Olsson M, Niklasson B, Wilson L, Andersson C, Christiansson R, 2004. Äspö HRL. Experiencesof blasting of the TASQ tunnel. SKB R-04-73, Svensk Kärnbränslehantering AB.
Olsson M, Markström I, Pettersson A, Sträng M, 2009. Examination of the Excavation Damaged
Zone in the TASS tunnel, Äspö HRL. SKB R-09-39, Svensk Kärnbränslehantering AB.
Peck R B, 1969. Advantages and limitations of the observational method in applied soil mechanics.
Geotechnique, 19, pp 171–187.
Pusch R, Ramqvist G, 2007. Borehole project – Final report of Phase 3. SKB R-07-58, Svensk
Kärnbränslehantering AB.
SKB, 2007. Final repository facility. Underground design premises/D2. SKB R-07-33, Svensk
Kärnbränslehantering AB.
SKB, 2008. Site description of Forsmark at completion of the site investigation phase. SDM-Site
Forsmark. SKB TR-08-05, Svensk Kärnbränslehantering AB.
SKB, 2009a. Design premises for a KBS-3V repository based on results from the safety assessment
SR-Can and some subsequent analyses. SKB TR-09-22, Svensk Kärnbränslehantering AB.
SKB, 2009b. Underground design Forsmark. Layout D2. SKB R-08-116, Svensk Kärnbränsle­
hantering AB.
SKB, 2009c. Site engineering report Forsmark. Guidelines for underground design. Step D2.
SKB R-08-83, Svensk Kärnbränslehantering AB.
SKB, 2010. Ramprogram för detaljundersökningar vid uppförande och drift av slutförvar för använt
kärnbränsle. SKB R-10-08, Svensk Kärnbränslehantering AB.
Wimelius H, Pusch R, 2008. Buffer protection in the installation phase. SKB R-08-137, Svensk
Kärnbränslehantering AB.

70

TR-10-18

Appendix A
Tabulation of data from measurements of as-built volumes in thetunnel excavated by means of smooth-blasting techniques at theÄspö Hard Rock Laboratory
For further details see Section 5.2.2
The following definition apply. The cross-sectional area of the experimental tunnel, 18.9 m2, is thenominal cross-section.
The experimental data are presented in Table A-1. The quantified cross-sections are those actually
measured and refer to the beginning and end of the blasting rounds, respectively. The round depths
are the actual measured and not the planned. The excavated volumes above the nominal were
calculated from surveyed tunnel profiles with one metre spacing. The aim was to position the drill
at the nominal tunnel profile at the start of the contour holes. The look-out angle, which defines
the theoretical completion of the contour hole, was 200 mm and 250 mm as shown in Table A-1.
The look-out angle creates an additional volume outside the nominal that gradually increases along
the length of a blast round. This space will be occupied by the drilling equipment when drilling is
ongoing for the next blasting round.
Table A-1. Experimental data based on /Malmtorp et al. 2009/.
Blasting round

Actual crosssectional area start[m2]

Actual crosssectional area end[m2]

Actual depth of
blast round[m]

Excavated volume above the nominal
[m3]

6

–

21.0

4.1

7

20.5

24.0

4.1

41.8
Look-out angle were 200 mm

8

21.3

22.6

4

9

21.0

23.4

4.6

10

20.5

22.8

4.6

11

21.2

22.4

3.6

12

21.5

–

3.0

Mean

21.0

22.9

Key parameters Overall mean = 22.0

TR-10-18

Sum = 27.9

46.6
Look-out angle were 250 mm

Average cross-section(18.9 x 27.9+41.8+46.6)/27.9 = 22.1 m2

71

Appendix B
Tabulation of data from measurements of cross-sectional centre
points and diameters in 6 deposition holes drilled at the Prototype
Repository at the Äspö Hard Rock Laboratory
For further details see Section 5.3.2
In the experimental trial, at every 400 mm of drilling the theoretical centre point was determined
for the cross-section in question. This enabled calculation of its deviation. Deviation was defined as
the horizontal distance between the theoretical centre point of the cross-section and a reference line
between the theoretical centre point at the bottom of the hole and the theoretical centre point at the
top. The calculated deviation in cross-sectional centre points can be regarded as an estimation of thestraightness of the deposition hole. The maximum deviation in the deposition holes can be assessed
to be less than 10 mm as shown in Figure B-1.
Experimental data – Prototype Repository

Top cross section
centre point

10

Deviation relative to local
coordinate system (mm)Measureddeviation

Bottom cross section
centre point

5

-10

-5

0

0

5

10

-5

-10

Deviation relative to local coordinate system [mm]Figure B-1. Deviation was defined as the horizontal distance between the theoretical centre point of thecross-section in question and a reference line between the theoretical centre point at the bottom of the holeand the theoretical centre point at the top. This measure can be regarded as an estimation of the straightness of the deposition hole. Calculation results showing the maximum deviation value are plotted for eachdeposition hole.

TR-10-18

73

Table B-1. Measured diameters in 6 Deposition holes drilled for the Prototype Repository

Borehole DA3587G01 (hole No. 5)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

Diameter (mm)
1-4
2-5
3-6
1,758
1,767
1,752
1,758
1,752
1,767
1,748
1,757
1,757
1,758
1,762
1,757
1,758
1,762
1,757
1,758
1,762
1,762
1,763
1,767
1,757
1,758
1,762
1,757
1,763
1,762
1,757
1,758
1,762
1,757
1,758
1,762
1,762
1,758
1,767
1,762
1,758
1,762
1,757
1,758
1,757
1,757
1,758
1,762
1,757
1,763
1,762
1,757
1,758
1,762
1,757
1,757
1,758
1,757
1,758
1,767
1,757
1,758
1,767
1,762
1,758
1,757
1,757
1,758
1,762
1,757

Mean diam for the borehole

mean
1,759
1,759
1,754
1,759
1,759
1,761
1,762
1,759
1,761
1,759
1,761
1,762
1,759
1,757
1,759
1,761
1,759
1,757
1,761
1,762
1,757
1,759

1,759

Borehole DA3575G01 (hole No. 7)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

Diameter (mm)
1-4
2-5
3-6
1,763
1,763
1,757
1,758
1,763
1,757
1,758
1,763
1,752
1,758
1,763
1,752
1,763
1,763
1,757
1,758
1,758
1,757
1,763
1,763
1,757
1,763
1,763
1,757
1,758
1,763
1,762
1,758
1,768
1,757
1,763
1,763
1,752
1,758
1,758
1,757
1,758
1,758
1,762
1,763
1,763
1,762
1,758
1,763
1,757
1,763
1,763
1,757
1,758
1,763
1,762
1,757
1,758
1,763
1,763
1,763
1,757
1,758
1,763
1,762
1,763
1,763
1,757
1,758
1,763
1,757

Mean diam for the borehole

74

mean
1,761
1,759
1,758
1,758
1,761
1,758
1,761
1,761
1,761
1,761
1,759
1,758
1,759
1,763
1,759
1,761
1,761
1,759
1,761
1,761
1,761
1,759

1,760

Borehole DA3581G01 (hole No. 6)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

1-4
1,764
1,759
1,759
1,764
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,764
1,759
1,759
1,764
1,764
1,759
1,759
1,759
1,759
1,764
1,754

Diameter (mm)
2-5
3-6
1,759
1,759
1,754
1,754
1,754
1,759
1,759
1,759
1,764
1,759
1,759
1,754
1,759
1,754
1,759
1,754
1,759
1,764
1,759
1,754
1,759
1,759
1,764
1,759
1,759
1,759
1,759
1,759
1,764
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,754

Mean diam for the borehole

mean
1,761
1,756
1,757
1,761
1,761
1,757
1,757
1,757
1,761
1,757
1,759
1,762
1,759
1,759
1,762
1,761
1,759
1,759
1,759
1,759
1,761
1,756

1,759

Borehole DA3569G01 (hole No. 8)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

1-4
1,759
1,764
1,759
1,759
1,759
1,754
1,759
1,764
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,759
1,764
1,759
1,759
1,754

Diameter (mm)
2-5
3-6
1,763
1,761
1,763
1,761
1,763
1,756
1,768
1,761
1,763
1,761
1,763
1,761
1,763
1,756
1,763
1,756
1,763
1,761
1,768
1,761
1,763
1,756
1,763
1,761
1,763
1,756
1,768
1,756
1,768
1,756
1,768
1,761
1,768
1,756
1,768
1,756
1,763
1,751
1,763
1,761
1,763
1,756
1,758
1,751

Mean diam for the borehole

mean
1,761
1,763
1,759
1,763
1,761
1,759
1,759
1,761
1,761
1,763
1,759
1,761
1,759
1,761
1,761
1,763
1,761
1,761
1,759
1,761
1,759
1,754

1,760

TR-10-18

Table B-1. Measured diameters in 6 Deposition holes drilled for the Prototype Repository (continued)

Borehole DA3551G01 (hole No. 9)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

1-4
1,752
1,752
1,752
1,752
1,757
1,747
1,747
1,747
1,742
1,747
1,747
1,742
1,747
1,747
1,737
1,742
1,742
1,742
1,737
1,742
1,747
1,742

Diameter (mm)
2-5
3-6
1,761
1,762
1,766
1,757
1,756
1,762
1,761
1,767
1,766
1,767
1,756
1,767
1,766
1,767
1,766
1,767
1,771
1,777
1,766
1,767
1,766
1,767
1,771
1,762
1,771
1,767
1,766
1,772
1,771
1,767
1,781
1,767
1,771
1,777
1,771
1,767
1,766
1,767
1,771
1,772
1,766
1,772
1,761
1,767

Mean diam for the borehole

TR-10-18

mean
1,758
1,758
1,757
1,760
1,763
1,757
1,760
1,760
1,763
1,760
1,760
1,758
1,762
1,762
1,758
1,763
1,763
1,760
1,757
1,762
1,762
1,757

1,760

Borehole DA3545G01 (hole No. 10)

Depth (m)

0.00
0.40
0.80
1.20
1.60
2.00
2.40
2.80
3.20
3.60
4.00
4.40
4.80
5.20
5.60
6.00
6.40
6.80
7.20
7.60
8.00
8.15

1-4
1,755
1,760
1,760
1,760
1,760
1,755
1,765
1,765
1,765
1,765
1,765
1,770
1,765
1,765
1,765
1,760
1,765
1,765
1,770
1,770
1,765
1,765

Diameter (mm)
2-5
3-6
1,757
1,756
1,762
1,756
1,762
1,756
1,757
1,756
1,757
1,756
1,762
1,756
1,752
1,761
1,767
1,756
1,747
1,756
1,767
1,756
1,757
1,756
1,762
1,761
1,757
1,761
1,757
1,756
1,762
1,756
1,757
1,751
1,752
1,756
1,757
1,751
1,762
1,756
1,762
1,756
1,757
1,751
1,757
1,751

Mean diam for the borehole

mean
1,756
1,759
1,759
1,758
1,758
1,758
1,759
1,763
1,756
1,763
1,759
1,764
1,761
1,759
1,761
1,756
1,758
1,758
1,763
1,763
1,758
1,758

1,759

75