■l

VlN

Nl▲N

3)

▲SI

N

a⊃JaLuLuO⊃ lO IUauJUDdaq ･S･n 'uo!lDJlS!u!LuP∀ I6olOUu⊃al

A60lOuqnl Pun SPJE}PuDIS lO aInI.llSuJ lDuO!IE}N

LO M･LOdl

一ヽ.上≡l N■JOITPヨ̀utZuJJmZ〇 ●V uaqdalS

e96 uO!11!3!tqnd tt!P3dsェsIN

凱IT133m luTOf PuZE 3ql JO S凱ITP33〇OJd●

SIJaJJ耳3!uS!aS Ptn! PtI!ノ仏ヽl

DEVELOPMENT OF SEISMIC ISOLATION TECHNOLOGYFOR UNDERGROUND STRUCTURES AND THE APPLICATION
byshigeki UNJOHl', Junichi HOSHIKUMA:', Kazuhiro NAGAYAnand Takeyasu SUZUKIJ)

ABSTRACTconstmction be reduced.

The seismic isolation for underground structures
is the system in which a tunnel body is coveredby a thin isolation layer00nsistmg of elastic

To meet these needs, the Public Works
Research Institute of the Ministry ofConstruction, the Public Works Research Centermaterials with low shear modulus. The isolationand 17 pnvate companies have taken part inlayer absorbs the strain transmitted from theJOmt research to develop seismic isolation
technology for underground stnlCtureS aS a new

surrounding sons during large earthquakes sothat the seismic pe血mance of undergroundtechnology that can improve the earthquake

structures be improved. ne Public Works

resistance of underground stmctures over that

Research Institute has developed this newprovided by conventional tectmologleS at theseismic isolation technology with the Public
Works

ResearchCenterand17

same time as it lowers constmction costs 'トH

prlVate00mpanies丘om 1995‑1998. Then the seismic

The seismic isolation structure that was

isolation technology lS applied for a practicaldeveloped for undergrollnd stmctures is aconstrction at the connection of vertical shaft

structurethat can sharply reduce the effects ofand tunnel of co血on utnity ducts firstly in theearthquakes by formmg a aexible seismic

world. This paper presents the outline of theisolation layer around the outerperiphery of all

seismic isolation technology and the practicalunderground structure to insulate theunderground structure from deformation of theapplication.

su汀Oundi皿g ground.

KEY WORDS: Seismic Isolation
Underground StnlCtureS

This paper describes an outline of seismic

Seismic Performanceisolation technology for underground structures

Common Utnity Ducts

and a practical application for the starting

verticalshaft of the Nakagawa UtilityTunnel･
A皿

1. ImODUCTION

Outline of也e test constmction of theseismic isolation structure as weu asthe丘eldtest to veri& the seismic isolation functions are

ne Hyogo‑ken Nanbu Ebrthquake of Januarypresented･

1995 damagedunderground structures and someunderground structures such asthe00llapse of

the DaikaiStation onthe Robe Rapid Transit
Ranway were heavily damaged. It is essentialto
guarantee

the operadon of commmication,

electricity, gas, water,and other lifelines inregions Struck by powerful earthquakes. To
achieve this goal,the safety

from strong

earthquakes of ututy tunnels that are typicalunderground structures provided to00ncentrate

1) Head, Earthquake Engineering Division,
Earthquake Disaster Prevention ResearchCenter, Public Works Research hstitute,
Ministry of Construction, Tsukuba‑shi,Ibaraki‑ken, 305‑0804, JapaJ12) senior Research Engineer, ditto

3) Research Engineer, ditto4) Deputy Director, Techical Institute ofthese lifeline services is required to be

Kumaga1‑gumi Corp., Tsukuba‑shi,preserved･And whilethe earthquake resistance

Ibarakli‑ken, 300‑2651, Japan(UndergroundStmcture Seismic lsolation Technology
promotion Committee)

of underground structures must be improved,
the public is demanding that the cost of their239

2. R良D OF SEISMIC ISOLATIONTECHNOLOGY

applied in 1) the longitudinal direction at pointsof abrupt change.in ground conditions, 2) where
the lateral sect10n Of a rectangular tunnel

Fig.1 shows a conceptual diagram of thechang.es abruptly,.and 3)in the longitudinal

seismic isolation structure, Seismic isolation

directlOn at COnneCt10nSwith verticalshafts, butmechanisms for underground structures are

the results of a cost‑effect analysis show that thecategorized under the followlng four items.

most promlSmg application of this seismic

1)Blocking the transmission of strain during

isolation structure is at the comections withverticalshafts of a shield tunnel.

earthquakes from the surrounding ground to atunnel structure2) smoothing the tunnel strain in the

The conventional me山Od of providing seismic

seismic‑isolated structure ( longitudinal

protection at connectionwithverticalshafts of adirection)

shield tunnel has been the application of a3) Dispersing the stress resultant coヮcentrated at

nexible segment･ Aflexible segment is a single

the corners of rectangular sectlOn tunnels

special(lateral direction)

concentrates and absorbs strain generated in the4)Insulating the vertical shaft body from thetunnel at the tumel entrance and smoothing thetunnel strain in the s.eismic isolated section (atverticalshaft coTmeCtlOn POints)

segment nng constructed so that it

surrounding tunnel･ A

flexible segment callabsorb turmel strainthat is locally concentrated
at the location where it is installed, but its

effects are generally limited to a smau range.

But if a verticalshaft is isolated from a segment

neperformance required by a seismic isolation

by a seismic isolation layer at the same time aslayer capable of providing these mechanisms

a seismic isolation layer is instauedwithin the

was

range

studied丘omtheperspective

of

its

where

the

groundstrainismostmechanical properties and construction

concentrated for about 10 m fromthe shaft, it isproperties, then the seismic isolation material

possible to provide isolation from botha point

was developed based on也e results of the study.

of abrupt change inne development process included testing tocorroborate the mechanical properties,

concentrated ground strain. h this way,thetumel stress resultant cam be reduced in a shortdurabnity, etc. of the seismic isolation material,

seismic isolation section.).

the structure and fromtesting to verify its construction properties bytrialmanufacturing a seismic isolation material
Injection system, azld corroborative material
Injection trials inanactualtunnel.And todevelop a seismic isolation Structure

3. PRACTICAL APPLICATION OF
DEVELOPED SEISMIC ISOLATIONTECHNOLOGY

construcdon method for shield turmels, inaddition to a seis血c isolation structure for use

3.1 Outline

at polntS Where ground00nditions change

ne seismic isolation structure forundergroundabruptly, a seismic isolation structure forstructures has progressed to the research andthat are pomts ofdevelopment stage, but be00use it has stiu not

abrupt chaJlge inthe structure and a method ofreached the stage wher￠ it is a practical designvertical

shaft

ComeCtions

constructing such a seismic isoladon structureand execudon teclmology, an actualstructure

havemust be designed and a trialexe印tion of血is

been

proposed.

A

designme血Od

andconstruction method for seismic isolation
structures for underground structuresthat has

design performed/

been established as a result of this joint researchh 1997, imitialseismic design for Ll earthquake

were put山shed in September 1998

motion was performed forthe verticalshaft
connection point of the No. 1 Nakagawa Utihty

as

the

Underground Structure Seismic Isolation Design
Method Manual (Draft) n

Tunnel (below referred to as "Nakagawa Utility
TunnelT'), and a nexible segment was chosen

The joint research has clearly shownthat theforthe start sideand a凸exible joint forthe

seismic isolation structure can be effectively

arrival side of也e00nnection poinL The NagoyaヽlNational Highway Construction Office of themethod (extemal diameter of the shield

Chubu Regional ConstnlCtion Bureau of themachine: 5,190mm) , and its segment ring joints

Ministry of Construction applied the field trial

were connected with long bolts. The tension

system, the connection was redesigned tostiffness of the shield tunnel was modeled uslng

provide seismic resistance capable ofequivalent tension st血ess calculated from thewithstanding L2 earthquakeL motion one rank

spnng of the segments and from the serial

higher than the previous design, and to confirm

sprlng Of the spnng of也e rlng JOlntS. The

the applicability of the new system in actual

compression stiffness used was the compression

tunnels and execution costs, this seismic

stiffness of the concrete of the segments.

isolation technology was selected for execution

on the No. 1 Nakagawa Tunnel in 1997. This

Because the external

was the first attempt to use this seismic isolation

machine wasstructure anywhere in the world.

isolation layer was set at 7cm that equals thediameter of the shield

5,190mm, the thicbess of the

thickness of the tail void.

3.2 Seismic isolation Design of VEticaI Shaft
The verification of safetyduring an earthquake

Connection(1) Struchlre Conditionsof the shield tunnel was performed based on

Fig.2 shows the surface ground structure at thetwo factors the allowed apemre Of the ring JOlnt

start side of the vertical shaft and the locational(2m) and the yield stress of the joint bolts

relationship of the verticalshaftand tunnel･ The(940N/mm2) during tension deformation, andbottom plate of the vertical sha氏is in a diluvial

based on the auowed compression stressclay layer, and the SMW wall diaphragm that

(24N/mm2)

surrounds it extends for about 40m down to acompression defbmation.

of

the

segments

duringdiluvialsandy so山layer. ne earthquake wave

Input bedrook and the bedrock of the(2) hput Earthquake Motion

axISymmetric finite element method model for

The input ea血quake motions f♭r L2 earぬquake

this design were assumed to be the top of也emotion were chosen from among standard

diluvialsandy soil layer Dsユ(V. = 320m/S) at

waves used for seismic design of highway

a depthof 30.9m in the figure. The figurealso

bridges･ Waves obtained by performingshowsthe mechanicalphysical properties during

amplitude compensation of也e00mponent at

sught strainofthe surface ground.

right angles tothe bridge axis of the Kaihoku

The vertical

Earthquake

Bridge duringthe MiyagiPrefecture Offshore
shafl is a reinforced concrete

structurewithextemalwidthof 14m and depth

of

1978

were

used

as

Type‑1of 10.8m and the plane shape shown at the top

earthquake motion for‑ category I ground. Waves
obtained by perfornngamplitude compensationof Fig.2. Its wall thickness varies somewhat

of也e NS00mponent re00rded at血e Robeaccording to the depthand it has partition wdls,

Marine MeteorologiCal

but because

dming

the overall shear sti血ess is not

Observation Station

the Hyogo‑ken Nazlbu Earthquake ofeffected by a∝ountlng forthese, it was assumed

1995

to be a box‑shaped s加Cture With a constantnotion･ Fig3(I) shows the Type‑1 earthquake

wallthickness of 14m for

motion and Fig.3(2) shows

this study. The

were used as the Type‑2

earthquake

the Type‑2

modeling of the vertical shaft by anearthquake motion. The one‑dimensionalseismic

axISyn皿etric fimite element method model

responseanalysis of the surface grotnd wasincludedthe modeling of not only也e vertiml

perfomed bythe substitute structure approach:shaft body, butconstructed by SMW as part of the vertiml

consideringthese nput earthquake motions to
be waves observed atthe outcrop offree rock,shaft.

reducingtheamplitude by 50%, aJld inputting

ne tunnel studied was a shield tunnel with anlayer Ddt The strain dependency of the groundexterior

also

the wall diaphragm

the resulting wavesfronthe top of the bedrockofused forthe analysis was obtained from a mean

reinforced concrete segments with a thickness of

stmin dependency evaluation equation for

250mm, it was constructed by the slurry shieldtyplCal ground 5) l)diameterof

5,050mmmade241

segment, the aperture exceeded the allowed
inertial force applied by thevalue･ The tension stress of the joint bolts was

axISymmetric finite element method model was

within the range of the allowed values for all

calculated by the ground response seismic

Cases.

ne ground

coefficient method7) that uses the groundacceleration at the time when the maximum
value of the total of the shear strain of theFig･6 shows the results ofananalysis during
compressive defbmation･ This figure shows thatground from the bed rock to the surface isunder both types of ea血quake motion, thegenerated based on seismic response analysIS･

compressive stress of the segment was within

the auowed value (940N/m2) for all cases. It
also reveals that adoptmg the seismic isolation(3) Design Results
Fig.4 shows the results of a parametric study ofstructure lowers the compressive axial fわrce on

deformation dming tension subject to strict

the segment to about ha止that obtained with thedesign conditions that was conducted torigid connection method, which is larger thandetemine the shear modulus of rigidity of thethe reduction t0 2/3 possiblewith aflexible

seismic isolation layer and the length of theSegment･

seismic isolation section. The variables for theparametric study were shear modulus of rigidity

Fig.7 is a schematic diagram of the seismicof山e isolation layer of O･3 and O･5N/mm: andisolation stmcture at the start vertical shaft

the length of the seismic isolation section fromestablished by

the exterior wall of the vertical shaft that were

design process. ne design calculations modeled

山e above seismic isolation

10, 15,and 20m. The sheanng modulus was set

the SMW and the vertiml shaft body as aconside血g silicon seismic isolation material

verticalshafL ne seismic isolation section that(SISMO̲003 or SISM0‑005) that is isolation

was analyzed extended for lOm

layer material

extemalwith superior durability andWall of the verticalfrom theshaft, but for

workabiuty.Analysis results have revealed that

execution reasons

wi也in a seismicauy isolated section length

segment length is 1.2m, the seismic isolation

between lOmand 20m,there is little variation
inthe tension axial force of the tunnel andthat

丘らm the tunnel entrance. Ths meansthat theeven if the shearng modulus of the seismic

seismic isolation section extended

isolation layer is reduced from O･5N/mmZ tothe externalWall of the SMW and 10. 5mfrom

o.3N/mZ, the tension axial force of the tunnel
declines very little. ne shearmg modulus of thethe externalwall of the verticalshaft body. On

includingthe fact that thelayer was formedinthe tail void for lOrings
9.6m fromthe ground side of the SMW wall,the seismic

seismic isolation layer was, therefわre, set at

isolation layer was 7血血ick血at is血e same as

0.5N/rmZand the seismiCal1y isolated section

the tail void, but it was thicker atthe entrance.

leng血was set at lOm丘om the exterior wan of

A且dthe SMW.

waterproof propertiesand to insulatethe verti001

Fig.5 showsanexaznple of the results of ananalysis of the joint aperture during tension

nng with a wedge‑shaped section,00Vered on

defbmation caused by Type‑1 ea血quakeamotion. h addidon to showlng the resultsfor aentrance Insulation layer) was installed at theseismic isoladon structtue case,the figure
presentsthe results of an analysis of arigid

turnel entrance and integratedwiththe tunnel

toprovide

the

tumel

entrancewi血shaft body丘om the segment, a natural mbber

three sides by water‑absorbingrubber, andwith
shea中gmodulusof

O･6N/mmZ((unnelentrance concrete.

connection caseand of a case hypothesizing a
且exible segment wi血a Young‑s modulus ofne adoption Of a seismic isolation structure as

0.1N/mml‑ at a point 1 mfromthe externalwall

described above, provides an existing structtlreofwith the ability to withstand Type L2

the vertical shaft. If a seismic isolation

stnlCture is adopted in this way,山e rmg JOmt

earthquake modon.And

aperture win be within the auowed value(2mm), but in the cases hypothesi2:ing the
adoption Of arigid connection and aflexible

function of the silicon seismic isolation material2142

the waterproo丘ng

guarantees waterproofing even if an
unpredictable joint aperture occurs.

ヽlmaterial is l･36, and its elongation is loo鞄. As

3.3 Practical Construction

stated above, the mix proportion was designed(1) isolation Material

to lower the shearlng mOdulus to less than 0.5

The seismic isolation material used for the trial

N/mm:. Therefore, when the seismic isolation

execution was silicon seismic isolation materialmaterial is shipped from the factory, it provides

SISM0‑005

JIS hardness of 32 degrees. and a shearlng

With

its

shearlng

mOdulusGadjusted to 0.5N/mmz or less. Silicon type

modulus of 0.44N/mmZ and satisfies theseismic isolation material is a mbber elastic

required physical properties after it has been

body hardened at normaltemperatures by theblended indoors based on the stlpulated mix

condensation reaction caused by mlXmg andproportion and is cured for one week at a

agltatlng瓜uid A that is a mixture of silicontemperature of 20 Centi‑Degree･polymer + finely powdered silica and ny ashwith nuid B that consists primarily of a(2) Construction

hardener and plastlClty adjustment agent at a

The level difference between the injection pump

mix ratio by weight of 10:1･ A cross linking

andinjection outlet was minimized, care wasagent is added unifわrmly to fhid A and ataken to obtaincatalysis is added to fluid B. It is, therefore,

fluid B, and the seismic isolation materialplanta stable blend offluid A andpossible to control o山y the hardening timewaswithout altermg the hardness of the mbber thatvertical shafL Fig.9 is a schematic diagram ofis the seismic isolation material by adjusting thethe seismic isolation stz.ucture at the start side ofquantity of the catalyst in fluid B. The seismic

the vertical shaft. As shown in the figure, theisolation materialisaninorganic materialbased

seismic isolation material was, in prlnCiple,

on silica and is both non‑pollu血g and durable.

ln)eCted during excavation from mjeCtion holes
in the segmentsinto the tan void produced as
the shield excavator advancedinthe same way
as immediate backfnling injection is performed･

Fig.8

shows the strain dependency of theshearlng mOd山us of the seismic isolationmaterialobtained by cyclic hollow cylindrical
cyclic shear testing performed at a loading
丘equency of lHz. This test showsthat theinstalled in anintermediate level of theIt was feared山at du血g the seismic isolationmaterial injection work, seismic isolation

seismic isolation materialhas stable dynamic

materialmightflow into the blades where it

physicalproperties regardless of the sheanngstrain. ne material has no constramg pressure

would get into the chamber. To preventthis
from occumng, aS the shield excavator(depth) dependency and it is an elastic material

advanced, void Blling clay (clay shock) was

witha danpmg factor lessthan3%0･

injectedintothe void betwee血its steel sheu andthe natural ground 'from an injection outlet

Fluid A is supplied tothe agitator (capacity

instaued near

the articulation of the shieldl･8m') of the plant ftont a hopper locatedabovethe ground,then it lS Pressure fed fromthe agitator at a fiJXed rate by a mono‑pump.

pressure injectednuid B is supphed tothefluid B agitator

excavated naturalground, italso preventedthe(皿PaCity 0.2m3) of the plant丘om a drum,thenseismic isolation material from leaking into theit is pressure fed fromthe agitator at a COnStantrate by a mono‑pump. The tip of the injector isnaturalground.

excavator to blockthe gap betweenthe tail voidandthe blade. Because･the clay shock was
into small voids on the

arubber injector used for backfin injection.

At locadonsAfter

pressmized feed hoses just before their

the

two

Auids

have

been

mked,

a

in

the

fluid A andfluid Bquarrymg coluzmmixer is passed througha

respective injection

2‑inch steel pipe for a totalof 80 cm and its

bypasses wereinstalled to cycle the two fluids

pressure loss is utilized to completely mix也ethroughagitators pnor to injection in order to

fluids. Because thismixer is long and it isdifficult to workwith,the injector unit andprevent separation ofand mⅨmg locations,

their materials and amixer are connected by aflexible ･rubber tube.

decline intheir viscosity. To form a seismic
isolation layer of uniform thickness around the

The specific gravity of the seismic isolationof the excavation. It was necessary to guarantee

segments, it wasvitalto exercise strict control

243

that the seismic isolation work would not

lower than the results of the measurementS at

con伽ctwiththe basic prlnCiples of shield work

the factory (hardness of 32, shearing modulus

that require the immediate filling of the tail voido.45N/mm:). The mean hardness of the seismic

to prevent the collapse of the natural ground andisolation material after 1 month passed, was 31

to keep out ground water and mud. To(G = 0.42N/mmZ), a result thatfully satisfied

guarantee this, before the work began, thethe design value of G = 0･5N/帆: or less･segments were equlpped with叫ection holes at
山ree locations in the tunnel axis direction that

(4) Field Test for EfreetivetleS Verificationdiffers for each segment piece, and injection

To verifythe seismic isolationperformance of

was begun from the injection hole closest to thethe seismic isolation stmcture fわrmed at thevoid, topermitthe restartmg of exmVation after

verticalshaft cormection by this trial execution,

it was stopped because of trouble w仙the work.

a field experiment was carried out to measure
the shear reaction force in the tunnel axis

That part of the work to form the seismic

direction of the seismic isolation layer.When aisolation structure at the vertical shaft

seismically isolated shield tunnel surrounded byconnection that was most important and had toa seismic isolation layer is forcefully deformed

be done wi也the greatest care was the work atin the tunnel axis direction, shear resistancethe entrance:the first stageinthe execution.
Because a large void is formed behind the

proportional to the shear reaction of theperiphery of the tunnel is obtained･ Because thissegment at the entrance as shown in Fig.9, it

sheaf reaction fわrce is the shear resistance of thewasseismic isolation layer and也e ground around it,

血st stabilized by f血ing it with highdenslty mud･ A丘er exmVation to the thirdring,

it is possible to evaluate it based on their series

clay shock was lqeCted to fu the void behindspnng system. If the sheanng modulus of thethe steel shell of the shield ex田vator to prevent

seismic isolation layer is more than 2 Orders

the seismic isolation material from凸owmg lntO

smaller than也at of the ground, it is possible tothe blades, then the injection of the seismic
isolation material atthe entrance was performed.

seismic isolation layer body

approximate

山e shear reaction fわrce of the也at treats theground as arigid body･ Consequently, uslng the(3) Quality Control

reaction force of the wall of the verticalshaft,

To00ntrol the quality of the seismic isolation

the tunnel was moved towards the cutting facematerial, the hardness of a hardened sample ofthe seismic isolation materialmade atthe time it
was shipped fromthe factory andthe hardness

along with the shield excavator by a hydraulicjack, andthe shearspnng constant of theseismic isolation layer was estimated from theof hardened samples made before, during, andrelationship of thr

tunnel axial

after injection were measured by the

defomation with

thmst of也e hydraulic

JIS‑K6301‑A method. ne

j ack.

seismic isolation

flow rates of

申uid A and

the

the

direction

fluid B were

controlled byinstalling Coriolisflow meters,

The shear spnng constaLnt Of

and the quantities offluid A

且uid B

isolation layer can be ob血ed theoretically byremalnlng intheir respecdve tanks afterthe
nJection work were measured to confirm thatEq.2from the relationship betweenthe force
andthe displaoement produced by treatugthe

the fLuids were completely injected.

periphery of the seismic isolation layer as aandthe seismic

constant00ndidon and forcefully deforming theⅥ血e也e mea皿

hardness of也e seismic

isolation naterialwhen it was shipped from thefactory was 32,the hardness of samples ofseismic isolation material obtained at the tip oftheinjector in皿ediately before, during, andafter lnJeCtion and cured for 1 week ranged
frorn

26

to

Conver血g

33

this

and
to

the mean value wastheshearing

29.

mOdulusobtained a result of 0.39N/nm , which is a little

extemalsurface of the humel in the tunnel axial
direction.

jこ= 2がGJln血/良) ♯ L(1)

Where:&: shear spmg constant of血e seismic

isolation layer
G‑: shear modulus of也e seismic isolation

layer

2

ヽヽ

244

エ: length of the seismic isolation layerヽヽ

凡: 1/20f the external diameter of theseismic isolation layer
R,:

I/2

0f

the

extemalpressure by another

400kN step･ When thehydraulic jack pressure was down to zero, thediameteroftheresidual displacement of the tunnel wasmeasured. The jacks were operated from antunnelintermediate level in the vertical shaft at a

Because it was necessary to complete thelocation where the operator

Injection of the seismic isolation layer at theloading device equlpped with the movable

startmg vertical shaft connection to fわrm thereaction frame.

00uld see theseismic isolation then perform this test before

the backful injection that accompanies normal
shield excavation,山e test was pe血rmed four

The cuttlng face slurry pressure wasautomatically regulated so that it remained at adays after the finalday of the seismic isolation

constant level of 0.15MPa (reaction of 3,200kN

material叫ection work.

to by the slu汀y pressure)血oughout allloading

andunloading steps. But during theFig･10 is a schematic diagram of the seismic

loading steps,the cutting face slurry pressure

isolation layer reaction force measurement test.

temporarily rose to a maximum of 0.17MPa aJld

The reaction receiver instaued on the verticalit took time to lower it to its stable value. But

shaft body wall was a mobile structure thatduring unloading, the cutting face slurryauowed the removal of the bolts to cause thepressure remained stable at almost exactly

temporary segment reaction frame to slide

O･15MPa, With the result that the puuing phasetowards the tunnel. The reaction receiver wasof the loading operation did not take as long as

equipped witha pedestal to be used toinstau

the pushing phase.

eight hydraulic jacks. By removlng its bolts andreceiver be00mes a loading device structurauy

The measurements were performed bymomitorlng the pressure and stroke of the 8equlPPedwitha movable reaction frame. As

hydraulic jacks, the relative axial

stated above, the periphery of the shielddisplacement of the segment andthe verdcnl

installing jacks on

the pedestal, the reaction

direction

excavator is血ledwith clay shockand it isshaft body on the left andright sides of theassumedvertical也at

血e shear resistance of也eshaft entrance, and the cutting face

periphery of the shield excavator is low. It was,slurry pressure in the centralcontrol room,and

therefore, possible to movethe segment inthe

by measunng the distance between the verdcnl

theshaftand the mg 1 joint of the segment closest

shield excavator tothe location wherethe shear

to the cutting face using a light measure system
fixed at the verticd shaft portal. ne data

direction of the cutting facealongwith

reaction fわrce of也e seismic isolation layer andthe jack thrust were in balance, by advaAClng
receiver and at the same time, adjustmg theobtained from these measurenents was
displayed tothe QPeratOr inthe intermediatelevel of the vertiml shaftand used to make jackcuttmg face slurry Pressure downwards tooperatng decisions. It wasalso nonitored andpreventthe action of the jacks frozn increasing

recorded

the hydraulic jacks instaued on

the reaction

this pressure to maintain it at a constant level.

ina measurement vehicle located at

ground level.

ne lacking pressure wasincreased at steps of(4) Test Resdts

50kN steps per jack for a total of 400kN per

Fig.ll sumarizesthe results of the testinstep･ ne jacking presstue was inαeased agam

terms of the relationship of the reladve拡ial

thedirection displacement of the tumelandthe

previous increase inthrust had stabniZ:ed. neverticalshaft body wall atthe entrancewiththe

load中g was concluded whenthe tumel had

totalthrust P1 0f the 8 jacksinstalled onthe

afler

the tunnel deformation caused bybeen defomed lO汀皿tOWardsthe cutting face･reaction frame･ ne hysteresis inthis figure is

ne unloading was performed in the same way

categorized as 5 loading states from I to V toasthe loading: reducingthe pressure applied by
the jacks by 400kN, waiting for the tunnel

spnng constant of也e seismic isolation layer.

deformation to stabnize, then lowerlng

While

the

245

explain也e process of detemlnmg山e shear

the behavior varied according to theloading stage as shown in Fig.ll, the tunnel

thestopped at location F with residual displacement

8,730kN/cm.

tunnelandits

sprlngCOnStantRL=

of approximately 1.57mm without being
restored to its orlglnal position even after the

Because the mean ln)eCtion rate of the seismic

jack pressure was finally reduced to zero at theisolation material was approximately 120%, theend of the unloading steps･

seismic isolation layer co汀eSpOnding to thisWith the residual displacement of the tunnel atof the shear sprlng COnStant Of the seismic

location F represented byisolation

Injection rate is 8cm, and the theoretical value
6 cm, the shear

layer

with

a

shear

modulusG=spnng00nstant of the seismic isolation layer by

0.5N/mm: is ll,380kN/cmZ based on Eq.(1).

RL (kN/cm) , the maximum static friction force

Because the measured shear spnng constant ofof the temporary segment and the pedestal by

the seismic isolation layer is 8,730kN/cm, theP.･Bt･t, and the cuttlng face pressure produced by
the cuttlng face slurry pressure by Pn･4, and

0･383N/rT‑I, Which conforms almost perfectly

assumlng that the cutting face slurry pressure

with the mean value of O39N/mmZ of thecan be ignored because in static state, it isseismic isolation materialinjected as describedshear modulus of the seismic isolation layer isIbalanced withthe slurry pressure, thefollowlng

above following 1 week of aglng. ne Shear

equation of equilibrium can be established forspnng00nstant and the shearmg mod山us of thethe pout in time where the tunnel has stopped

seismic isolation layer are, therefore, appropnate

atthe final stage･

values.

K.=6

+

pd..

:

p,,.,.,(2)

be concluded that because the residual

Because as described above, elastic behavior

displacement ♂ ≡ 0.157cm, the max血um static

capable of restonng the tunnel to its original

It can丘iction force is in balancewith(reaction force

position during unloading m a linear relationship

P･d Produced by the cutting face slurry pressure

with the jack thmst was obtained and because
the sheanng mOdulus of the seismic isolation≡ 3,200kN) + (reaction fわrce of the seismic

isolation layer equivalent to the shear

layer is an appropnate value, it has been

deformation of 0.157rm). Next, if it isassunedthat the point A in Fig.ll corresponds

verified that a seismic isolation layerwith theintended functions was constnlCted.

to the tine when the temporary segment began

to sude on the top of the pedestal, the maximum
static friction force P.,.,k = 4,570kN,and if these

4. CONCLUDING REMARXS

values are substituted in equation (2), &(kN/cm) is as shown below.
jこ= 4,570

This paper has su丘marized the design and

3,200/0.157 = 8,730(3)execution of a seismic isolation stnlCture fわr

underground structures山at has been made at

nethick dark lineinFig.ll showsthe results

the start verdcale shaftconnection of an actualof assummg that P,..,k = 4,750kN and jこshield tunnel.

=

8,730kN/cm to estimate the hysteresis(1) ne trial execution of the seismic isolation

relationship of the jack thrustwiththe axial

structtue verified the execution properties of thedisplacement of the tunnel whenthe reaction

snicon seismic isolation material

force at

System.

the cu出ng face is assumed to beconstant. ne hysteresisthat was estimatedshows a separation from actualbehavior caused
by instabiuty of the cutting face soil pressure at

injection(2) ne mean injection rate of the seismic

loading stage Ⅲ 15), but the fact that bothisoladon materialis 120%, which is a rate lower
than the injection rate of nomal backfill.
(3) In‑situ testing conducted to measure theconform closely at loading stage IIand at Vthat

reaction fわrce of也e seismic isolation layer

was the丘nal stage of the unloading andanveri丘ed thealmostlinear load displacement relationshipstructure by demonstratmgthat elastic behavior
capable of restoring the tunnel to its original

was obtained during unloading reveals that aseismic isolation layer wi血reliable resilient

behavior was formed around th'e periphery of

1､

246

functions of the seismic isolation

position during unloading m a linear relationshipwith the jackthrust could be obtained and thatヽL

the sheanng modulus of the seismic isolation

stmctures (partlayer obtained by the test

Seismic isolation Design Manual, Joint

00nfbrms with

3), Underground Structure

Research Reports, Reference No･ 211, Sept･

measured values.

(4) The above results have shown that this1998 (in Japanese)

seismic isolation structure for underground4) shigeki Unjoh, et.al.: Seismic Isolation

structures is a teclmology that canbe applied to

StnlCtureS and Seismic Isolation Design ofthe design and execution of actual underground

Underground Structures, Proceedings of the

Sixth Tunnel Engineering Research Conference,
vol･ 8, pp･ 31‑38, 1998 (in Japapese)5) public Works Research lnstltute: Numericalstructures.

ACENOWLED CEMENTS

Analysts Of Response Properties of GroundThe constnlCtion of the seismic isolation

Document No. 1778, Febmary 1982 (instructure was pe血rmed wi血Japanese)

During Earthquakes, ‑the generous

assistance and cooperation of the staff of the
Nakagawa Shield Tunnel Construction Office,liazama‑Sato Joint Venture under the contract

DESTRA‑, PWR

6) Yasuda, Yamaguchi: Dyn.amic Deformation

Properties of Various Categones of Undisturbed
Son, Twentieth Soil Engineenng Researchof Nagoya Construction OfBce of Ministrry ofconference, pp.539‑542, June 1985 ( inConstruction. The authorswish to conclude by

Japanese)

expressing their sincere gratitude to them for

7) Katayama kuo et. al.: Proposalof the■'Response Seismic Coefficient Methodt' atheir contribution to this prqect. The membersof the Underground Structure Seismic Isolation
Teclmology Promotion Committee provided

Practical Quasi‑dynamicAnalysis Method fortechnicaladvice regarding the plammg andthe

Technical Conference of the Japan Society ofStructures Buried Underground, FortiethAmual

design of the trialexecution. ne authors wish

civil Engineers, Part 1, pp.737‑738, 1998 (into also山ank them for their assistance.

Japanese)

8) Takeyasu Suzuki et.al. Dynamic Properties
of Snicon Seismic isolation Material for Tunnel
REFEREN CES

Seismic Isolation Work, Proceedings oftheThirty‑second Conference on Ground1) public Works Research hstitute, et.al.:
Report on Joint Research on the Developmentof Seismic Isolation Materials for Use in

theEngineering, pp.2095‑2096, 1997 (in Japanese)
9) Takeyasu Suzuki, et.al.: ExperimentalStudyof Silicon Material for UrbanTunnel Seismic

Seismic lsolation Design of Undergroundlsolation Structures, ℃ouected Reports of theStructTreS (Part 1) , Joint Research Reports,
Reference No. 154, Nov. 1996 (in Japanese)

Japan Society of Civil Engineers, No･
534〝Ⅰ‑30, pp.69‑76, 1996 (in Japanese)2) public Works Research hstitute, et.al.:

10 Shigeki Unjoh, et.al.: Function Verifimtion

Report on Joint Research on the Development

Testing of Seismic Isolation Structures for Useof Seismic Isolation Materials l'or Use

at VerticalShaft Connections, Collected Papers
and Reports on Tunnel Engineermg Research,
vol. 9, 1999 (inJapanese)

in

the

Seismic Isolation Design of Underground
Structures (Part 2), Joint Research Reports,
Reference No. 192, Dec. 1997 (in Japanese)ll) shigeki Unjoh, et.al.: Draft Manual for3) public Works Research hstitute, et.al.:

Seismic Isolation Design for Underground

Report on Joint Research onthe Development

Strucutres, Proceedings ofof Seismic Isolation MaterialS

Meeting on Windand Seismic Effects, U∬寸R,

亡=■for Use in

theSeismic Isolation Design of Underground

247

NIST SP931, August 1998

the‑㌔ 30thJoint

TatrunエPtZで耶qS Tで〇!UaA叩JO lnOAn z･軸

saJn3〇叫S PunO血apun JOJ侶0‑ompaエuO叩OSI叩S!aS l･軸g弼o知抑(r品)uo!tenTaU V

知和o和(L .3)uo!)cJ3tDU V

一1.

JA

0

5

10

15

20

25

30

5

10

Tirne (see)1520Time (see)(2) Type‑2(1) Type‑1

Fig.3 Input Earthquake Motion

1

つ乙

00

(Nq)3U‑OdL .!rVuO!SuaL

一一一Rigid 僂ozlneCtion N/rnm,.10m

1 000′ノ一一ヽ‑L､..

停ﾓ‑G‑0.5

一一一一G‑0.3 ‑‑G‑0.5 ‑.‑G‑0.5 披 ﾓ"ﾃ

ﾒ 鬻ﾗ｢ Vﾒ 鬻ﾖﾓ"ﾒ

8000
L". ■●■ー ●■一一▼

ｨ耳

ｸ

R

剪

6000
JJ‑‑

4000
2000

ｨ耳

7鉅

H耳耳+U

し ●1 ̲ ●1̲̲̲ 定

ﾈ璽

l!/
l

0
0

1

0

20

30

40

50

Distan∝ from ExtemalWdl of Vertical Sha允(m)Fig.4

Effect of Shear Modulus andLength of Seismic lsolation layer

22110 5 0 5 ∩U 5
II一●■

TYPE‑1I I I I I I

｢

ﾂ

ﾂ

劔

(E )巴n)hadvIU!0(

TJ.Jf L 劔劔‑‑‑‑‑RigidConncction ‑‑‑ncxibleSegncnt ‑Seismiclsolation 劔劔

1

I

50

100

DislanCC from ExlemalWdl of WcrticalShaft (m)Fig･5

AnalysIS Of Ring Joint Aperture

249

25

30

1

三二二二′ Ji

(NI)3 ‑OL三e!XV3^!S aJduou

∫
r

■ヽ ‑1

睦至萱]

劔

‑‑‑RigidConncction ‑‑‑‑FlexiblcScgment ‑Scismiclsolation 劔剪l r I ● tl l I I I

I

I

0

tL 一‑

ｨ爾

ﾂﾒ

綴

ﾂ

●

ﾂﾒ

劔剪

(

I ̲i‑

ll

椿ﾆﾅ

劔剪

:ニー̲

勇､ﾂﾒ

50

100

150

Distance from Extcmal Wall of Ve山cal Shaft (m)Fig.6

Analysis of Compressive AxialForce of Segments

Styrofoam Blo ck≡:.:::..;.:.;:;:.:::‑;:scismicLs .‑.:.../...... 柳ﾆ F柳 匹ｲ罐ﾖ亦顋 ｹ｢d‑‑一■■■■lllll■‑lllll■■‑‑■I‑一一一→■■■■■‑J‑l‑一■■

Fig.7

Seismic Isolation Structure at Start Vertical Shaft

1 ･〇 〇･8 0･6 0･4 0･2l(. ∈∈＼N)DSntnPOM】苫エS

ff■SISM0‑5l劔∫

0.0001

0.001

0.01

0.1

1

Shear StraizL T

Fig.8

Strain Dependency of Shear Modulus of Silicon Seismic Isolation Material

250

lSZ

1Saエ)UatmmSe9M pla!d JOつ叩tmq〇S Ol●苛!J･.A

110!1〇9.rtll tBp叩M tIO叩lOSI 〇!tHS!aS IIO〇mS

6'冨!dFig･)tJackHF2StndJhialTuneDisplacmentRlaioshp

JhaJTuzuelDisplacenenI(日n)

犯

03

ﾂ

ｸ

*2

粨耳

ﾂ

ﾂ

(刀

r1

剪

剩

喜
l

2

白

萱

剪

LLJ

g;

u⊃

剪

劍8ﾖﾂ

i

ql 剪

1 冩N 劍耳耳
"ー司 庖D"

(

*ﾔｦﾂ

､､J

剪

ー＼p 剪

＼

rTltD

礼

B

′‑〜.

rO

＼

ゝ＼

闔ｨ

抱

§

6r簫粨爾

喜

6r粨爾

鳴

價8

I

§

ト.‑■

lー

ト.･.■

⊂〉

薙

＼＼

*D｢

ト一

LD

､､｣

の

Un

J>

(

〜

ド

LJ}

｢1

)

Total Thrust of Hydraulic Jacks (kN)･ﾄB

So