Large Scale Experiments of Permanent Ground Deformation Effects on

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					Large Scale Experiments of
Permanent Ground Deformation
Effects on Steel Pipelines
               by Koji Yoshizaki, Thomas D. O’Rourke, Timothy Bond, James Mason and Masanori Hamada

 Research Objectives
  The objectives of the research are to: 1) simulate in the laboratory full-   National Science Foundation,
                                                                                  Earthquake Engineering
scale permanent ground deformation (PGD) effects on steel pipelines with
                                                                                  Research Centers Program
elbows, 2) develop an extensive and detailed experimental database on          Tokyo Gas Company, Ltd.
pipeline and soil reactions triggered by earthquake-induced PGD, and 3)        National Science Foundation,
refine and validate analytical models so that complex soil-pipeline interac-      U.S.- Japan Cooperative
tions can be numerically simulated with the precision and reliability nec-        Research for Mitigation of
essary for planning and design. To accomplish these objectives, an                Urban Earthquake Disasters
international partnership was organized, involving the Tokyo Gas Com-
pany, Ltd., MCEER, and NSF through its program for US/Japan Cooperative
Research in Urban Earthquake Disaster Mitigation. The project combines
experimental and analytical research performed at Tokyo Gas facilities with
                                                                               Koji Yoshizaki, Pipeline
experimental and analytical work undertaken at Cornell University. The
                                                                                 Engineer, Fundamental
experiments at Cornell represent the largest simulations of PGD effects          Technology Laboratory,
on pipelines ever performed in the laboratory.                                   Tokyo Gas Company, Ltd.
                                                                               Thomas D. O’Rourke,
                                                                                 Thomas R. Briggs Professor

D     uring earthquakes, permanent ground deformation (PGD) can dam-
      age buried pipelines. Earthquake-induced PGD can occur as sur-
face fault deformation, liquefaction-induced soil movements, and land-
                                                                                 of Engineering, Timothy
                                                                                 Bond, Laboratory Manager,
                                                                                 and James Mason,
slides. There is substantial evidence from previous earthquakes, such            Graduate Research
as the 1983 Nihonkai-chubu (Hamada and O’Rourke, 1992), the 1994                 Assistant,
                                                                                 Department of Civil and
Northridge (O’Rourke and Palmer, 1996), and the 1995 Hyogoken-
Nanbu (Oka, 1996) earthquakes, of gas and water supply pipeline dam-             Engineering, Cornell
age caused by earthquake-induced PGD. More recent earthquakes,                   University
including the 1999 Kocaeli and Duzce earthquakes in Turkey, and the            Masanori Hamada,
1999 Chi-chi earthquake in Taiwan, have provided additional evidence             Professor, Department of
of the importance of liquefaction, fault rupture, and landslides through         Civil Engineering, Waseda
their effects on a variety of highway, electrical, gas, and water supply         University
   Gas and other types of pipelines must often be constructed to change
direction rapidly. In such cases, the pipeline is installed with an elbow
that can be fabricated for a change in direction from 90 to a few de-
grees. Because elbows are locations where flexural and axial pipeline

                           deformations are restrained, con-     performed as part of MCEER Pro-
                           centrated strains can easily accu-    gram 1 on the Seismic Retrofit
                           mulate at elbows in response to       and Rehabilitation of Lifelines and
• Cambridge University     PGD.                                  the NSF program for U.S./Japan
                              The response of a pipeline el-     Cooperative Research in Urban
• Kyoto University         bow, defor med by adjacent            Earthquake Disaster Mitigation.
                           ground rupture and subject to the       MCEER has a long history of
• Rensselaer Polytechnic
  Institute                constraining effects of surround-     productive collaboration with the
                           ing soil, is a complex interaction    Japanese earthquake engineering
• University of Southern   problem. A comprehensive and          research community. Seven U.S./
  California               reliable solution to this problem     Japan workshops on the earth-
                           requires laboratory experiments       quake performance of lifeline fa-
• University of Tokyo      on elbows to characterize their       cilities and countermeasures
                           three-dimensional response to         against liquefaction have been co-
• Yamaguchi University
                           axial and flexural loading, an ana-   sponsored by MCEER, and the
                           lytical model that embodies soil-     proceedings of these workshops
                           structure interaction combined        have been published and distrib-
                           with three-dimensional elbow re-      uted by MCEER. The latest in this
                           sponse, and full-scale experimen-     series of workshops (O’Rourke, et
                           tal calibration and validation of     al., 1999) was held in Seattle, WA
                           the analytical model.                 in conjunction with the 5th U.S.
                             To resolve this problem, an in-     Conference on Lifeline Earth-
                           ternational team was organized.       quake Engineering. The next
                           The principal participants are To-    workshop is planned during the
                           kyo Gas Company, Cornell and          forthcoming year in Tokyo, Japan.
                           Waseda Universities.The research      U.S. participants in the work-
                           also involves the University of       shops include MAE, MCEER, and
                           Cambridge, UK, Rensselaer Poly-       PEER researchers.
                           technic Institute, and the Univer-
                           sity of Souther n Califor nia.
                           Waseda University leads a consor-     Experimental and
                           tium of Japanese university par-      Analytical Models
                           ticipants that include Kyoto and
                                                                   One of the deformation condi-
                           Yamaguchi Universities and the
                                                                 tions of interest is illustrated in
                           University of Tokyo.The work was
                                                                 Figure 1a that shows a pipeline

                                The users of this research include: public and private util-
                              ity companies, including gas distribution companies, such
                              as Tokyo Gas and Memphis Gas, Light and Water; and water
                              distribution companies, such as the Los Angeles Department
                              of Water and Power (LADWP), and the East Bay Municipal
                              Utility District (EBMUD). The research is also of interest to
                              engineering design and consulting companies. The experi-
                              mental data and analytical modeling procedures developed
                              for this project are of direct relevance for underground gas,
                              water, petroleum and electrical conduits.

with an elbow subjected to PGD         associated with lateral spread,
consistent with lateral spread         landslides, and fault crossings, and
and/or landslides.Although lateral     therefore applies to many differ-
spreads and landslides involve         ent geotechnical scenarios. In ad-               Program 1: Seismic
complex patterns of soil move-         dition, the experimental data and                    Evaluation and Retrofit of
ment, the most severe deforma-         analytical modeling products are                     Lifeline Networks
tion associated with these             of direct relevance for under-
                                                                                        Program 2: Seismic Retrofit of
phenomena occurs at the elbows         ground gas, water, petroleum, and                    Hospitals, Task 2.7a, Cost
and near the margins between the       electrical conduits.                                 Benefit Studies of
displaced soil mass and adjacent,        A modeling technique, named                        Rehabilitation Using
more stable ground.The deforma-        HYBRID MODEL, was developed                          Advanced Technologies
tion along this boundary can be        for simulating large-scale pipeline
simplified as abrupt, planar soil      and elbow response to PGD
displacement. Pipelines that can       (Yoshizaki et al., 1999 and 2001).
be sited and designed for abrupt       The model uses shell elements for
lateral displacement will be able      the elbow where large, localized
to accommodate complex pat-            strains occur. Shell elements are
terns of deformation that fre-         located over a distance of 20
quently involve a more gradual         times the pipe diameter from the
distribution of movement across        center point of the elbow. The
the pipeline. Abrupt soil displace-    shell elements are linked to beam
ment also represents the principal     elements that extend beyond this
mode of deformation at
fault crossings.
  Figure 1b illustrates
the concept of the
large-scale experiments.
A steel pipeline with an
elbow is installed under
the actual soil, using
fabrication and compac-
tion procedures encoun-
tered in practice, and
then subjected to                (a) PGD Effect of Buried Pipelines with Elbows
abrupt lateral soil dis-                          Compacted sand
placement. The scale of
                                         Welded steel
the experimental facil-                    pipeline                                                  1.3m
ity is chosen so that
large soil movements
are generated, inducing                            5m
                                                                                 Displacement of
                                                                                   Movable box : 1.1 m
soil-pipeline interaction                                Fixed box
unaf fected by the               (b) Experimental Concept
boundaries of the test
facility in which the
pipeline is buried. The I Figure 1. Experimental Concept for PGD Effects on Buried Pipelines with Elbows
ground defor mation
simulated by the experi-
ment represents defor-
mation       conditions
                            Large Scale Experiments of Permanent Ground Deformation Effects on Steel Pipelines
                                                                              even when the opposing ends of
                                                                              the elbow were deformed into
                                                                              contact with each other and
                                                                              strains as high as 70% were mea-
                                                             G                sured. In contrast, leakage was ob-
                                                    .B                        served in the opening mode for
                                                                              all cases except those in which
                                                                              the deformation was restricted
                         D         E
                                                                              because of the experimental load-
                                                                              ing device. The HYBRID MODEL
                                                                              was used to simulate the deforma-
                                                         F                    tion behavior of the elbows using
                                                                              linear shell elements. Very good
                                                                              agreement was achieved between
                                                                              the analytical and experimental
                                                     H                        results for all levels of plastic de-

    Movable box
    Teflon sheet
                                                                              Large Scale
    Fixed box                  C
    100-mm-diameter pipe       D
    90-degree elbow            E                                                Figure 2 shows a plan view of
    Pulley system              F
    Sand storage bin
                                                                              the experimental setup that con-
    Data aquisition system     H                                              sisted of five main components,
                                                                              including a test compartment (A
                                                                              and C in the figure), pulley load-
I   Figure 2. Plan View of Experimental Setup                                 ing system (F), sand storage bin
                                                                              (G), sand container hoisted from
                                                                              storage bin to test compartment
                                                                              (not shown), and data acquisition
                                       distance. Soil-pipeline interaction
                                                                              system (H). The test compart-
                                       under PGD is characterized by p-
                                                                              ment was composed of a movable
                                       y and t-z cur ves, linking soil
                                                                              box (A) and fixed box (C) within
                                       stresses on the pipe to the rela-
                                                                              which the instrumented pipeline
                                       tive displacement between them.
                                                                              was installed and backfilled. The
                                       Lateral soil-pipeline interaction is
                                                                              L-shaped movable box had inside
                                       characterized on the basis of labo-
                                                                              dimensions of 4.2 m by 6m by 1.5
                                       ratory experiments originally per-
                                                                              m deep. It was constructed on a
                                       formed at Cornell (Trautmann
                                                                              base of steel I-beams positioned
                                       and O’Rourke, 1985) and dupli-
                                                                              over Teflon sheets that were fixed
                                       cated at Tokyo Gas experimental
                                                                              to the floor. The Teflon sheets
                                                                              provided a low-friction surface on
                                         In-plane bending experiments
                                                                              which the movable box was dis-
                                       were conducted by Tokyo Gas
                                                                              placed by a pulley loading system.
                                       (Yoshizaki et al., 1999 and 2001)
                                                                              The fixed box, which was an-
                                       on full-scale specimens of steel el-
                                                                              chored to the floor, was designed
                                       bows in both the closing and
                                                                              to simulate stable ground adja-
                                       opening modes. No leakage was
                                       observed in the closing mode,

cent to a zone of PGD similar to
that illustrated in Figure 1.
  A 100-mm-diameter pipeline
with 4.1-mm wall thickness was
used in the tests. It was composed
of two straight pipes welded to a
90-degree elbow (E). The short
section of straight pipe (D) was
5.4 m long, whereas the longest
section was 9.3 m. Both ends of
the pipeline were bolted to reac-
tion walls.The elbows were com-
posed of STPT 370 steel (Japanese
Industrial Standard, JIS-G3456)
with a specified minimum yield
stress of 215 MPa and a minimum
ultimate tensile strength of 370
MPa. The straight pipe was com-
posed of SGP steel (JIS-G3452)
with a minimum ultimate tensile
strength of 294 MPa. About 150
strain gauges were installed on
the pipe to measure strain during
the tests. Extensometers, load
cells, and soil pressure meters
were also deployed throughout
                                        I    Figure 3. Overhead View of Test Compartment Before(top) and
the test setup.                             After (bottom) an Experiment
  The pipeline was installed at a
0.9-m depth to top of pipe in each
of four experiments. In each ex-
periment, soil was placed at a dif-
ferent water content and in situ        container that was hoisted with
density.All experiments were con-       the overhead conveyor. The sand
ducted to induce opening-mode           was placed and compacted in
deformation of the elbow.               150-mm lifts with strict controls
  The experimental facility was         on water content and in situ den-
designed with the assistance of         sity. One of the most significant
the HYBRID MODEL that was               challenges during the testing was
used to simulate various testing        the movement and controlled
configurations and compartment          placement of such large volumes
dimensions. Significant character-      of sand with water content that
istics of the experimental facility     was intentionally changed for
are its size and volume. The stor-      each experiment.
age bin for the sand was over             The movable box was pulled by
three stories tall, with a capacity     an overhead crane with an 8 to 1
for 75 tons. Approximately 60           mechanical advantage obtained
tons of sand were moved from the        through the pulley system shown
storage bin into the test compart-      in the figure. The maximum ca-
ment for each experiment with a         pacity of the loading system was
                         Large Scale Experiments of Permanent Ground Deformation Effects on Steel Pipelines
                                                                     simulations discussed in the next

                                                                     Analytical and
                                                                     Experimental Results
                                                                       Finite element analyses were
                                                                     conducted with the HYBRD
                                                                     MODEL to check the ability of the
                                                                     analytical simulations to capture
                                                                     key aspects of the pipeline and
                                                                     elbow response to abrupt lateral
                                                                     displacement. Figure 5a compares
     I   Figure 4. Overhead View of Deformed Experimental Pipeline   the deformed pipeline shape of
                                                                     the analytical model with mea-
                                                                     sured deformation of the experi-
                                                                     mental pipeline. There is
                          1 m of lateral displacement and
                                                                     excellent agreement between the
                          784 kN. The rate of displacement
                                                                     two, and there is obvious agree-
                          of the movable box was approxi-
                                                                     ment between the analytical de-
                          mately 16mm/s.
                                                                     formation and the overhead view
                            Figure 3 shows the ground sur-
                                                                     of the deformed pipeline in Fig-
                          face of the test compartment be-
                                                                     ure 4. Figure 5b shows the mea-
                          fore and after an experiment.
                                                                     sured and predicted strains under
                          Surficial cracks can be seen in the
                                                                     maximum ground deformation on
                          area near the pipeline elbow and
                                                                     both the tensile (extrados) and
                          the abrupt displacement plane
                                                                     compressive (intrados) surfaces
                          between the movable and fixed
                                                                     of flexure along the pipeline. Fig-
                          boxes after the test. In all cases,
                                                                     ures 5c and d show the measured
                          planes of soil slip and cracking
                                                                     and analytical strains around the
                          reached the ground surface, but
                                                                     pipe circumference in which the
                          did not intersect the walls of the
                                                                     angular distance is measured from
                          test compartment to any appre-
                                                                     extrados to intrados of pipe, cor-
                          ciable degree.
                                                                     responding to 0 and 180o, respec-
                            Figure 4 shows an overhead
                                                                     tively. In Figure 5d, the data point
                          view of the test compartment af-
                                                                     with an upward arrow indicates
                          ter soil excavation to the pipeline
                                                                     the maximum strain measured
                          following one of the experiments.
                                                                     when the gauge was discon-
                          Because each experiment was run
                                                                     nected during the experiment. Be-
                          until a total displacement of about
                                                                     cause the disconnection occurred
                          1m, the analytical models can be
                                                                     before maximum deformation of
                          tested and calibrated through a
                                                                     the elbow, it is likely that the ac-
                          broad range of deformation and
                                                                     tual strain was larger than the
                          strain in the elbow. The deformed
                                                                     value plotted. Overall, there is
                          shape of the pipeline can be seen
                                                                     good agreement for both the mag-
                          clearly in the figure. Its shape is
                                                                     nitude and distribution of mea-
                          remarkably consistent with the
                                                                     sured and analytical strains.
                          shape shown by the finite element

  The large-scale
                                                                                                                     Experiment (extrados)
have provided a                                                                                                      Experiment (intrados)
                                                                                    40                               FEA (extrados)
rich and compre-                                                                                Elbow                FEA (intrados)
hensive database

                                       Distance from the corner
for understand-                                                                     20

                                                                                        Strain, %
                                   -4             FEA                                                                               Lp

                                              to east (m)
ing pipeline re-
sponse to large                                                                      0

PGD, particularly                   0

under conditions                    2                                              -20
                                      -10    -8     -6      -4    -2      0    2        0               5               10              15
where local con-                        Distance from the corner to south (m)               Distance from the east edge, Lp (m)
straint at an el-          (a) Deformation of the pipeline after the test         (b) Distribution of axial strain in the longitudinal
bow leads to
complex three-                                   Experiment (Longitudinal)                             Experiment (Longitudinal)
                                                 Experiment (Circumferential)                          Experiment (Circumferential)
dimensional re-                                  FEA (Longitudinal)                                    FEA (Longitudinal)
                                                 FEA (Circumferential)                                 FEA (Circumferential)
sponse and high
                                20                                                      40
strain concentra-
                                                A     A                                                    B
tions. Although
                                                      Section A-A
the interpreta-                 10                                                      20                       B
                                        Strain, %

                                                                                                    Strain, %
                                                                                                             Section B-B
tion of the ex-                                                                         10
perimental                       0                                                       0
results is still in
progress, the data
have      already              -10
                                     0         45         90         135      180
                                                                                            0         45         90        135         180
shown that, with                                  Angle, (degree)                                         Angle, (degree)

appropriate                (c) Strain distribution at the cross section of the    (d) Strain distribution at the cross section of the
                               connecting part between the elbow and short               elbow (Section B-B)
modifications,                 leg of the straight pipe (Section A-A)
the current gen-
eration of analyti-
cal models is able
to simulate real      I Figure 5. Comparison Between Analytical and Experimental Results
performance in a
reliable way.
  One of the most important as-                  formation patterns in soil adja-
pects of the research has been to                cent to the pipeline during PGD
clarify the effects of moisture                  are significantly different for dry
content on the pressures gener-                  and partially saturated sand.
ated by soil-pipeline interaction
during PGD. Current analytical
models use p-y curves derived                                     Summary
from laboratory test results with                  Large-scale experiments spon-
dry sand. Virtually all sand in the              sored by Tokyo Gas were success-
field is placed with measurable                  fully completed to evaluate the
water contents that affect its in                effects of earthquake-induced
situ density and shear deforma-                  ground rupture on welded steel
tion characteristics. The large-                 pipelines with elbows. The ex-
scale experiments have shown                     perimental set-up involved the
that the failure surfaces and de-                largest full-scale replication of

                                   Large Scale Experiments of Permanent Ground Deformation Effects on Steel Pipelines
     ground deformation effects on                 planned in the forthcoming year
     pipelines ever simulated in the               to investigate further the p-y char-
     lab.The tests allow for calibration           acterization for partially saturated
     of a sophisticated soil-pipeline in-          sand as a function a water con-
     teraction analytical program de-              tent and compaction effort. Work
     veloped in conjunction with the               also is planned with collaborating
     experimental work. The experi-                universities for developing the
     mental data and analytical mod-               next generation of analytical
     eling products are of direct                  model that will represent the soil
     relevance for underground gas,                as a continuum with specific con-
     water, petroleum, and electrical              stitutive relationships capable of
     conduits.                                     simulating large ground deforma-
       Additional work at Cornell                  tion and its interaction with bur-
     sponsored by Tokyo Gas is                     ied pipelines.


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     Yoshizaki, K., Hosokawa, N., Ando, H., Oguchi, N., Sogabe, K. and Hamada, M., (1999),
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     Yoshizaki, K., O’Rourke, T. D. and Hamada, M., (2001), “Large Deformation Behavior of
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