LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures
17-19 November 2015

The adequate variable of deterioration rate
prediction formula about a polyvinyl chloride pipe
T.Miyamoto*,
W.Fukatani,T.kaya,
D.takeuchi, T.Yokota
National Institute for Land andInfrastructure Management, Japan

Background2

Current situation of sewer pipes in Japan

14,00012,00010,0008,000
6,000

Others45

Polyvinyl Chloride Pipes

40

Ceramic Pipes
Concrete Pipes
Accumulation length
period of higheconomic

35
30
2520
15

4,000

102,000

500

Accumulation length（10,000km）

16,000• There are now about 10,000km of pipes
older than 50 years, and sewage pipes
are aging rapidly.

50Before1950
1953
1957
1961
1965
1969
1973
1977
1981
1985
1989
1993
1997
2001
2005
2009
2013

Length by year of construction（km）

18,000⇒ Deteriorated pipes areconcrete and ceramic currently.
• PVC pipes were developed later.
⇒ Few surveys

The properties of the PVC pipe
deterioration must be clarified.
Factors contributing to ‘degree ofemergency’ must be evaluated.

Total length by year of construction
by type of pipe in JapanLESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

3Approach of this study
collect the results of surveys of PVC pipes
clarify the deterioration
phenomena of pipes

clarify the relationship ofpipes conditions with defects(propose a new inspection standard)clarify the relationship ofdegree of emergency with defects

to develop the deterioration curve of PVC pipes

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

4Defects that appear on PVC pipes
Grease slime, 22

Mortar, 42

Root intrusion, 55

Projection, 126
Inverse curvature,54

Deformation, 499Infiltration, 813

Sag, 977

Breakage, 118
Crack
Circumferential, 26
Displaced, 163

4115 spans were analyzed.
The results of surveys of PVC pipes (conducted by Local government )LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

5Major and specific deterioration phenomena on PVC pipes

phenomenons
typical offlexible pipe
Deformation

Inverse curvature

Cracking in the pipe axis direction
quickly causes breakage of pipes.

Breakage
LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

6Evaluation
oftotal span

New diagnostic items for PVC Pipes
Rank
Item

Application

Vertical sag

Pipe d iameter
less than 700mm
Rank
Item

Evaluation of each pipe

Breakage and Axial d irection CrackABC

Diameter or overHalf d iameter or over

Below half d iameter

ａｂｃ

――

Complicated Crack
Axial d irection Crack

Crack Circumferential

5mm or over

2mm or over

Below 2mm

Displaced

Open joint

Half con n ection len g th or overBe low half conne ction le ngth

Deformation

15% d eformation withflexib ility factor or over

5% d eformation withflexib ility factor or over―

Inverse curvature※（ Projection on insid e surface）

10% d iameter or over

Below 10% d iameter―

Infiltration

Splashing

Flowing

Bleed ing

Projection

Half d iameter or over

10% d iameter or over

Below 10% d iameter

Grease slime

Half diam eter or over blocked

Be low half d iame te r b lock e d―Root intrusion

Half diam eter or over blocked

Be low half d iame te r b lock e d―Mortar

30% diam eter or over blocked

10% diam eter or over blocked

Be low 1 0 % d iame te r b lock e d※The inverse curvature with the whitening of materials assumes it a rank

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

7

What kind of pipes conditions are correlated with defects ?
Defects occur on PVC pipes
What kind of pipes condition should be considered
to develop the deterioration curve ?
Pipes conditions correlated with defects○ To count the number of occurrence locations per 1km for each defectdivided by pipes conditions(depth, years of service, pipe diameter, etc.)○ To analyze the relation between pipes conditions
and number of deterioration occurrence locations.

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

8Example1 (depth and number of deterioration locations)
Number of locaion of defectper kilometer(location/km)

45
40
35
30
25
20
15
10
50Breakage

Crack
Circumferential

Displaced
Joint

Infiltration

Root intrusion

Inversecurvature

Deformation

DefectLess than 1m

1-2

2-3

3-4

4m or more

○ 4m or more, ‘Infiltration’ occurred more frequently.
○ Less than 1m, ‘Root intrusion’ occurred.
○ In proportion to depth, ‘deterioration’ occurred.
The results showed different trends acceding to each defect.
LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

9

Number of locaion of defectper kilometer(location/km)

Example2 (Pipe diameter and number of deterioration locations)
121086420Breakage

Crack
Circumferential

Displaced
Joint

Infiltration

Defect150mm 200mm

Root intrusion

Inversecurvature

Deformation

250mm○ ‘Deformation’ have relation to the diameter.
○ Other, there is no clear relationship.
LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

10Pipes conditions correlated with defects
Sag
Severe defects have occurred mainly on pipes buried at relatively
shallow depth (1-3m).
Deformation
Within the range of pipe diameter from 150mm to 250mm,
the more deteriorated locations existed.
In proportion to depth, ‘deterioration’ occurred.

The results showed different trends acceding to each defects,
and to the condition of pipes.

Based on the ‘degree of emergency’ calculation method,
we tried to clarify what kind of defect should be considered.
LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

11

Degree of emergency calculation method
Evaluation of total
span

Evaluation of each pipe

Vertical Sag(Evaluated as A,B,orC）

Breakage and Axial direction Crack , Crack Circumferetial ,Displaced , Infiltrarion , Projection , Grease slime ,Root intrasion , Mortsr , Deformation , Inverse curvature（Projection on inside surface）(Evaluated as a , b , or c）

Evaluation of total span based on defect rate（Note １）
Defect rate of rank"a"＝total number of rank"a"／number of pipes in 1 supan
Defect rate of rank"a+b"＝total number of rank"a" or "b"／number of pipes in 1 supan
Defect rate of rank"a+b+c"＝total number of rank"a","b" or "b"／number of pipes in 1 supan
Defect rate of rank"c"＝total number of rank"c"／number of pipes in 1 supanAB

CRank"ａ" defect rate 20% or over,or rank"a+b" defect rate l40% or over ,OR
Fracuture rank"a" and deformation
rank"b" or more , or displaced rank"a"(Note2)Rank"ａ" defect rate less than 20% ,or rank"a+b" defect rate less than 40% ,or rank"a+b+c" defect rate 60% or overNo rank"a"or"b" ,and rank"c" defect rate less than 60%ABC

Judgment in emergency(Judgment in totals of A，B and C）
Emergency Ⅰ Span evaluation A for 2 items or more items
Emergency Ⅱ Span evaluation A for 1 items or span evaluation B for 2 items or more items
Emergency Ⅲ No span evaluation A , span evaluation B for 1 or span evaluation CNo Deterioration Sound condition without anyy span evaluation CLESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

12

Degree of emergency calculation methodEmergency

CategoryⅠ

An early treatment is required

ⅡA required can be postponed up to 5 years by a plain action

Ⅲ

A required can be postponed over 5 years by a plain action

No Deterioration----------

Totally, 4115 spans were collected.
○ Emergency Ⅰ：
In a past survey the authors conducted, no such spans could be discovered○ Emergency Ⅱ：
There are 221 spans to analysis.
○ Emergency Ⅲ：
There are 1329 spans to analysis.

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

13

Contribution rate to degree of emergency by determining factor(emergency Ⅱ)
𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝑜𝑜𝑜𝑜 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑏𝑏𝑏𝑏 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 (%) =𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠
64%

29%
Degree of emergency II is a case wheredefect occurrence rate A or sag A haveoccurred in a span.

Sag A only
20%

Sag A andDefect B
5%

Defect A only49%

Sag A andDefect C
4%
Sag B andDefect B
7%

Defect Aand Sag C
13%
Defect A andSag B
2%

The percentage that defect occurrence
rate A has contributed at this time isabout 64%, which is 29% higher thanthe percentage contributed by sag A.

Which defects contribute to
the defect occurrence rate A?

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

14

Contribution rate to degree of emergency by determining factor
𝑑𝑑𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 % =4035

Contribution rate（%）

30𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑏𝑏𝑏𝑏 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟
𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠

Deformation, Breakage, and Infiltration
contribute to defect occurrence rate A.

2520151050DefectContribution rate case judged to be EmergencyⅡ（%）

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

15

Contribution rate to degree of emergency by determining factor(emergency Ⅲ)
𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷𝐷 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 (%) =65%

Sag B only
8%

54%

Defect B only21%

Sag C only
39%

Defect C only
14%
Defect Cand Sag C
12%

Sag B andDefect C
1%

Sag C andDefect C
5%

𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝑜𝑜𝑜𝑜 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑏𝑏𝑏𝑏 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑜𝑜𝑜𝑜 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑜𝑜𝑜𝑜 𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒𝑒 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠

There were many items that contributed todegree of emergency III,and the contribution rate was also thesame for the defect occurrence rate of 54%
and sag of 65%.

It is necessary to further analyze pipe
conditions that impact degree ofemergency III by determining factors.

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

16Summary
Even in PVC pipes with relatively few defects,
there are defects that result in early pipe failure.
so, appropriate inspections are required.
Defects that occur in PVC pipes are affectedby pipe diameter and depthlocations of deformation, breakage, and infiltration
are at high priority for repairs or other countermeasures.

It is suggested that these parameters, especially correlatedwith deformation, breakage, and infiltration, should beconsidered to develop the deterioration curve of PVC pipes.
LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

appendix

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015

17

18

Example3 (Years of service and number of deterioration locations)
Number of locaion of defectper kilometer(location/km)

14121086420Breakage

Crack
Circumferential

Displaced
Joint

Infiltration

Root intrusion

Inversecurvature

Deformation

DefectLess than 10 years

10 to 20 years

20 to 30 years

30 to 40 years

LESAM 2015 – Strategic Asset Management of Water and Wastewater Infrastructures 17-19 November 2015