Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, JapanSEISMIC PERFORMANCE ASSESSMENT OF EXPANSION JOINTSFOR WATER LIFELINES
Tomohiro HIGASHIDE1, Takahiro YABUGUCHI2, Toshio IMAI3 and Takeshi KOIKE4
1

Student, Department of Civil Engineering, Kyoto University,
Kyoto, Japan, tomohiro.h@ay7.ecs.kyoto-u.ac.jp
2
Engineer, Water Pipeline Division, JFE Engineering Co.,
Yokohama, Japan, yabuguchi-takahiro@jfe-eng.co.jp
3
Professional Engineer, Water Pipeline Division, JFE Engineering Co.,
Yokohama, Japan, imai-e-toshio@jfe-eng.co.jp
4Professor, Department of Civil Engineering, Kyoto University,
Kyoto, Japan, koike.takeshi.7n@kyoto-u.ac.jp

ABSTRACT: In the 2011 Great East Japan Earthquake, the largest water leakage flows
occurred at failed expansion joints in 2400mm and 1200mm diameter water pipelines in
Miyagi Prefecture. The damage mechanism of buried expansion joints was investigatedby site damage inspections and seismic response analyses, which suggested that the
expansion joints had absorbed certain settlement before the earthquake, and as a result,the seismic shaking triggered expansion joint failure. This study proposes a new seismic
design method for expansion joints, especially those used in arc-welded steel pipelines.
Key Words: Great East Japan Earthquake, expansion joint, pipeline, riser, seismic design

INTRODUCTION
Many water pipelines were damaged in the 2011 Great East Japan Earthquake. In particular, buried
expansion joints used in large diameter water main lines were broken, resulting in large-scale leakage
and suspension of water service for several weeks.
Generally, buried water pipelines suffer relative vertical displacement, which is forced by unevensettlement between the pipeline itself and the structural facility housing the control equipment, andrelative axial displacement caused by ground shaking. Both types of relative displacement areabsorbed by expansion joints, which are installed in the pipeline near the structural facility. Especiallyin water main lifelines, expansion joints are used not only in segmented pipelines but also in
arc-welded pipelines.
In this study, based on site observation of damaged joints2), the failure mechanism of buried expansion
joints was investigated by site damage inspections3) and seismic response analyses. The first event
caused large-scale leakage from a pair of expansion joints installed at the outlet of a concrete encasedunder-crossing structure. The second event of leakage damage from an expansion joint appeared
approximately one month later after the main shock. Both results had the common characteristics that
there was no typical ground deformation which could produce failure of the expansion joints, and1457

there was no additional deformation allowance for the seismic response of the joint because the joint
had absorbed a certain settlement before the earthquake. These investigations suggest the possibility
that buried expansion joints may change from safety devices to potential defects that can cause
leakage failure under seismic loading.
This study proposes a new seismic design method for expansion joints, especially those used in
arc-welded steel pipelines. The new method describes the adequate allocation of expansion joints andadditional deformation allowances for avoiding pull-out failure due to seismic displacement.

SEISMIC DAMAGE OF EXPANSION JOINTS IN WATER PIPELINES
Table 1 summarizes the damage data of buried large diameter water pipelines in the 2011 Great East
Japan Earthquake. The typical characteristics are1) leakage failure from the expansion joints5);2) leakage from old joints with poor welding quality dating from before1965;3) expansion joint failure between the concrete structure and surrounding soil which had alreadyundergone certain excessive relative displacement; and4) wrong application of expansion joints in soft ground based on the former JWWA design guideline.
Among these, the largest water leakage flows occurred at failed expansion joints in 2400mm and1200mm diameter water pipelines in Miyagi Prefecture. Both pipelines are located in the southern partof Miyagi Prefecture, as shown in Figure 1, where the JMA seismic intensity4) in the March 11thearthquake was 6+, or approximately 250~400 cm/sec2. Figures 2 and 3 show the strong groundmotion at Shiroishi (nearest point to the sites) in the March 11th main shock and April 7th aftershock,respectively. As both pipelines are pressurized trunk lines which convey water to demand nodes, thepipe segments were carefully jointed to take into account possible uneven settlement due to various
soil conditions along the pipe route.

Table 1 Damage to buried large diameter water pipelines in 2011 Great East Japan Earthquake.7),8)

Location
Miyagi Pref.

DiameterDamage descriptions
Leakage and joint separation damages occur at the expansion joints of the
2400mmboth ends of under-crossing concrete structure.

Miyagi Pref.

Leakage occurs at the after shock after one month of the main shock at the
1200mm expansion joint located between the valve vault and the concrete covered
riser pipe.

Miyagi Pref.
Miyagi Pref.

1000mm Separation of the expansion joint between the concrete structures
700mm Leakage from the repaired welded portion

Fukushima Pref. 2000mm Separations of 12 expansion joints in the liquefaction area
Tie tod failure of the expansion joint by the excessive tension load caused by
the ground movement
Expansion joint failure at 25 locations in the liquefied zone of the purification
Ibaragi Pref.
variousplant
Leakage of 3 expansion joints which were designed with the SUS belows
Kanagawa Pref. 3100mm
type expansion joint based on the old design guideline.
Leakage from the welded joint crack. The same type of accidents have been
Kanagawa Pref. 600mm
experienced along this pipeline.
Ibaragi Pref.

1100mm1458

Location 2

Fig. 2 Strong ground motion at Shiroishi (MYG016)
in main shock (2011.3.11).

Location
1
漏水箇所
Fig. 1 Locations of leakage accidents.

Fig. 3 Strong ground motion at Shiroishi (MYG016) inaftershock (2011.4.7).

FAILURE MECHANISM OF THE EXPANSION JOINTS
Expansion joints under-crossing stream line
Photo 1 shows the large-scale water leakage from the expansion joint in the 2400mm diameter water
pipeline immediately after the main shock. The accident occurred at both sides of the concrete encased
pipeline under-crossing a water stream, as shown in Figure 4. It must be noted that this leakage
occurred at the same time from both expansion joints. The concrete encased structure moved700mm in
the anticlockwise direction at site A and 100mm
at site B.
VB φ2400×44°05'
VA 44°05'

VB φ2400×44°12'
VA 44°12'

排水管 φ2400×φ400

VB φ2400×5°52'
IA 5°52'100mm

伸縮継手 φ2400

Lower
side

A
CB φ2400×65°52'
IA 64°02' 28”
VA 20°53' 51”

VB φ2400×20°51'
VA 20°51' 25”

伸縮継手 φ2400

0m
=66.
工 L
防護

白石インター

D
Upper
side

Photo 1 Water leakage from expansion joint.

700mm

Fig. 4 Location map of expansion joints
under-crossing stream line.

1459

AS δ

N

A

kN1

2A

A’ δ1Aaθ
kE1

Fig. 5 Three-dimensional illustration of under-crossing
concrete encased structure.
According to site observations, there were no groundchanges triggering liquefaction, ground slippage or unevensettlement. As shown in Figure 5, this under-crossing
concrete encased structure has an unstable configurationand is not symmetrical even in the two-dimensional plan
view.

b

G

O’

O ψA

φ
φA

v

G’
E

u
c

kE2

xSN

d

xSE

D’
kN2

δ1D

D δ2D

Ds

Fig. 6 Two-dimensional simplified analytical model ofunder-crossing concrete encased structure.
In order to investigate the failure mechanism of the two expansion joints, a configuration describing a
two-dimensional simplified model of the under-crossing concrete encased structure is introduced, as
shown in Figure 6. The gravity point of the structural model is the origin of this figure, and the spring
moduli are adopted to simulate the soil-structural interaction of the buried structure. The direction of
the coordinate system is identical to the global direction. Since the expansion joints are structurally
separated from the concrete encased structure, joint failure occurs when the relative displacement
between the concrete encased structure and its corresponding stretching pipe exceeds the criticaldisplacement in the axial direction and/or transverse direction. To assess this criterion, the relative
displacements at the end points A and D are estimated by the following formula: a cos A 
 u  a cos( A   )  a cos A xSE  , A   , AS  
(1)
A  
 a sin  A 
 v  a sin( A   )  a sin  A  xSN 
in which A and A’ are the displacement vectors of the expansion joint at the original point A and at
the deformed point A’, but As is a displacement vector of the corresponding ground response at point
A. Relative displacement at the expansion joints is calculated by the following formula: x  u  acos  A  cos A    δ A   1 A   Q A  SE




sin

sin


x
v
a





A
A
 2A 
 SN
 cos A sin A 
Q A    sin A cos A (2)where a is the length from the origin (or the gravity center of AOD) of Figure 6 to point A, and  A
and  A are angles from the origin and from the bending corner of the concrete structure to point A,
respectively.
The structural responses of the two-dimensional displacement and rotational motions are obtained by
the following equilibrium equation of motion:  Ku  KxS
Mu(3)
where M and K are a mass matrix and stiffness matrix, respectively, which are given by

1460

M

M 0
0


0
M
0

0

0
I G 

,k E1  k E 2
0( k E1b  k E 2c ) sin  
kN1  kN 2
0
( k N 2c  k N 1b) cos K ( k b  k c ) sin  ( k c  k b) cosk E1b2  k E 2 c 2 
E2
N2
N1
 E1

(4)

and M , I G are the mass and rotational rigidity of the concrete encased structure, k N 1, k N 2 , k E1, k E 2 are
the spring moduli of the surrounding soil and these spring moduli are evaluated by the Seismic design
specification of highway bridges9), and b,c, are the length from the center of gravity of A’OD’ andstructural configuration angle.
The variables u and xs are the structural response and the free field ground response6) as given byu u  v
 
 

,

 xSE 
x S   xSN 
 0 



(5)

In the numerical analysis, the spring modulus was randomly modified from the original value tosmaller ones in order to obtain the largest responses that can exceed the limit boundary of the
expansion joint. Figure 7 shows the excessive displacements between the ground responses and thestructural responses in the axial and transverse directions at points A and D in Figure 6. 1 A and 1D
are the responses in the axial direction, and  2 A and  2 D are the responses in the transverse
direction, respectively. These figures show that the maximum response appears in the transverse
direction of point D, as shown by  2 D . This result does not conflict with the observation that the largest
movement at the encased concrete structure occurred at point D in the transverse direction. The second
largest response is given by  2 A , which might support the observation that both expansion joints were
simultaneously destroyed by the main shock. Figure 8 is the rotational response of the concrete
encased structure. These structural responses as shown by the triangular and square marks in themultiple limit state diagram for the expansion joint failure modes in Figure 9. In this figure, threedifferent performance limit curves are shown as boundary conditions of the joint failure. Here, two
modified performance curves were prepared for reduced allowance conditions which correspond toexisting settlement before the earthquake. The numerical results suggest that the expansion joints atthe site might have produced an existing settlement equivalent to 1/3 to 2/3 of maximum performance
before the earthquake.

Fig. 7 Excessive displacement between structural response and ground displacement at expansion joint
points A and D, where 1 is axial displacement and 2 is transverse displacement to the pipe axis.

1461

Fig. 8 Rotational angle of under-crossing concrete encased structure.

250
margin alpe rforman c e

200

A(lowe r side )150
D(u ppe r side )δ1100

2 / 3 modif ie dpe rforman c e
1 / 3 modif ie dpe rforman c e

50
0
0

50

100

150

200

250

300

350

δ2

Fig. 9 Multiple limit state diagram of expansion joint failure modes, in which modified performance
curves are generated from the marginal performance curve in deteriorated joint allowance states.

Expansion joint between valve vault and riser system
Leakage failure from an expansion joint occurred in the aftershock of April 7th, approximately one
month after the main shock. In this section, the discussion focuses on this one month delay in theaccident.
Photo 2 shows the damaged expansion joint in which leakage failure occurred at the upper portion of
the expansion joint. The sealing bolt and ring at the upper portion were hydro-blasted by high pressure
water and the half portion was worn out, as shown in Photo 3.
From this, the following failure mechanism could be deduced: (1)The main shock of March 11,2011
produced high pressure water leakage from a small gap in the joint; (2) this water leakage started towear the metal portion of the sealing parts, and this wear continued for one month; (3) the deteriorated
sealing ring could not stop the large scale leakage caused by shaking due to the aftershock of April 7th.
In order to confirm this failure scenario, the possibility that these failure steps could occur as a resultof the main and aftershocks must be evaluated by the numerical approach.

1462

Photo 2 Excavation of joint failure portion.

Photo 3 Sealing bolt worn out by hydro-blasting.

6550

3000

5500

550

φ900

3800

1500

1800

4900

600
200

1000

450

1500

EL=61.465

500

1300

1500

500

900

EL=58.075

250

EL=55.925

1400
1225 550

2700
5500

800 600
500 1275

16000

12700

9050

Fig. 10 Schematic illustration of riser and valve pit system
1200

EL=45.375
1500

弁室側
Valve
pit side

1500

plan
平面図

EL=42.375

170mm

60mm

.
Valve pit side
上流（弁室側）
250mm

390mm

1,230mmsection
断面図
3.5°

下流（立坑側）Riser side
1,350mm

立坑側
Riser
side

(a) Plan view(b) Sectional viewFig. 11 Site allocation of expansion joint after leakage.

1463

The expansion joint, which is located between the valve pit and the riser structure as shown in Figure
10, had a potential risk of uneven settlement, so that the expansion joint was forced to absorb verticaldisplacement. As a result of this settlement, the residual allowance for the seismic effect was limited.
Based on the site investigation on April 7th, 2011, different vertical settlements were measured at thetwo ends of the expansion joint, as shown in Figure 11. This suggests that the joint had rotated to anangle of 3.5 degree before the earthquake. Using the site soil conditions shown in Figure12, theseismic response of the concrete riser was analyzed with a single-degree-of-freedom system asfollows.
   2 M   ki
 x G    MxQ   k i ( x Q  x si )  k i li   

(6)
2
2 
 



k
x
l
x
k
l





k
l
I
k
k
l
i
si
i
Q
i
i




i
i
G
R
i
i






in which xQ , xG , xsi and  are base-rock ground motion, structural and surface ground responses,
and rotation angle, as shown in Figure 13, and, ki and li are the spring constant and the length at thei-th point from the gravity point. I G and k R are the rotational rigidity of the riser and its rotational
stiffness for the surrounding soil and structural interaction. Figure 14 shows the seismic responses of
the riser and the expansion joint in the main shock and the aftershock. In the main shock, themaximum rotation is less than 1 degree, which is not sufficient to destroy the expansion joint. This
response led to a small leak from the joint since the pre-existing settlement had already produced
rotation of 3.5 degree in the expansion joint. According to the fabricator’s specification shown in
Figure 15, the allowable maximum angle is 6 degree, so the main shock could not cause large-scaleleakage immediately after the main shock. However, one month after the first small leakage, thehydro-blasting effect had worked on the sealing ring, reducing the thickness of the bolt diameter andthe ring itself. As a result, when the second shock occurred in the aftershock of April 7th, the sealing
ring had already been worn out, and could easily be broken by a small impact. This is a reason the
expansion joint suffered a leakage failure in the aftershock.
In the second example, the pre-existing settlement played an important role in initiating small leakage
from the sealing ring, which caused hydro-blasting that reduced the metal portion of the sealing
elements. This result suggests that the allowable displacement of the expansion joint should bedesigned not only for vertical settlement under ordinary construction conditions but also forexcessive displacement by future earthquakes.

N値
N
value

00
0

silt
gravel

00

10

1

11

2

22

3

33

4

44

5

55

10
10
20

30

N-val

20
20
40

50

3030 4040 5050

xQ

66
深
さ(m)
depth
dept
7
77

(m)
h

8

silt

gravel

θ
li

6

sand

ki

xS i
xi

60

xG

88

9

99

10

10
10

11

11
11

12

12
12

13

13
13

14

14
14

15

15
15

x

Fig.12 Soil classification and N value at site

Fig.13 Configuration of the coordinate system for riser.

1464

(A1) Horizontal riser response in main shock.

(B1) Rotation 

in main shock.

(C1) Vertical response of joint in main shock.

(A2) Horizontal riser response in aftershock.

(B2) Rotation 

in aftershock.

(C2) Vertical response of joint in aftershock.

Fig. 14 Seismic responses of riser and expansion joint in main shock and aftershock.

eccentricityδFig. 15

Allowable angle of expansion joint for eccentricity .

PROPOSALS FOR SEISMIC DISASTER MITIGATION OF EXPANSION JOINTS
From these two leakage failure events, several points for the improvement7) of the seismic design
method for expansion joints are proposed, as follows:(1) Asymmetrical shape of a structure can produce unstable responses. Actually, in this example,
rotational motion caused simultaneous destruction of the expansion joints. Special attention should be
paid to the seismic design of asymmetrical structures.
(2) Generally, one set of expansion joints is installed at the two sides of a valve pit to absorb possible
uneven settlement. In this situation, the connected pipes are assumed to be buried in infinite stretches.
However, these pipes are often connected to other structures (a riser structure in this case) in the1465

vicinity of the valve pit. Therefore, it should be noted that the expansion joint must not be connected
to a pipe which may be subjected to additionally forced settlement.
(3) A routine design for the valve pit and expansion joints should always be assessed based on the total
allocation of the structures connected to the pipe from the valve pit.

CONCLUSIONSIn the present study, the failure mechanism, which resulted in large-scale leakage from expansion
joints of large diameter water pipelines in the 2011 Great East Japan Earthquake is investigated.
One event was triggered by rotation of a concrete encased structure which under-crosses a stream line.
The other event occurred approximately one month after the main shock. This delayed failure wasattributed to progressive damage of the expansion joint sealing ring by hydro-blasting, whichdeveloped from a small initial leak caused by the main shock. These two events were initiated by theseismic responses of the concrete encased structures, in which the one is a spatially developed rigid
structure and the other is a vertical rigid structure of a riser.
These examples show that pre-existing settlement and deteriorated performance must be taken into
consideration when studying possible failure mechanisms. These results suggest that it is important tomaintain an additional displacement allowance for future earthquakes, and to design a symmetricalconfiguration of the structure which cannot produce unpredicted failure modes.

REFERENCES
1) Japan Society of Civil Engineers: Great East Japan Earthquake urgent damage research report,
Chapter 10, Damage of water pipe facilities, 2011.
2) Sennan, Sen-en wide area water supply office: Outline of Sennan, Sen-en wide area water supply
business (http://www.pref.miyagi.jp/ss-kousui/index.html)
3) JFE Engineering Corporation: Great East Japan Earthquake damage of water pipe facilities-Sitesurvey report (2011.6.28), 2011.
4) National Research Institute for Earth Science and Disaster Prevention: Kyoshin Network K-net(http://www.k-net.bosai.go.jp/k-net/)
5) Water Steel Pipe Association: Expansion joint for water steel pipe, WSP 024-97, WSP, 1997.
6) Yoshida, N. and Suetomi, I.: DYNEQ, (Version 3.01), Sato Kogyo Central Research Institute,
1999.
7) Water Steel Pipe Association: Damage analysis of water pipe in Great East Japan Earthquake andsuggestion for recovery, 2011.
8) Water Steel Pipe Association: Water pipe facilities earthquake-proof method of construction
guideline and explanation, 1979 version, 1979.
9) Japan Road Association: Seismic design specification of highway bridges, 2002.

1466