Rational Earthquake-resistant Design and Maintenance of Buried Pipelines Conception rationnelle antisismique et entretien des conduites de gaz souterraines Koji YOSHIZAKI, Tokyo Gas Co., Ltd., Pipeline Technology Center, Japan Takashi SAKANOUE, Tokyo Gas Co., Ltd., Pipeline Technology Center, Japan Naoto HAGIWARA, Tokyo Gas Co., Ltd., Pipeline Technology Center, Japan 1. INTRODUCTION During earthquakes, underground lifelines such as buried gas pipelines can be affected by the surrounding soil. To maintain their function as lifelines supporting people s lives, and at least prevent disasters caused by leakage of the contents, it is important to consider the effect of earthquakes in the design and maintenance of such lifelines. The 1995 Hyogoken-Nanbu (Kobe) earthquake with a magnitude of 7.2 was caused by the activity of an inland active fault near a large urban area, the Hanshin district. The very strong seismic motions observed near the fault and subsequent Permanent Ground Deformation (PGD), occurring as surface fault deformation, liquefaction-induced soil movements, and landslides, significantly affected underground lifelines such as gas, water, sewage, electric power and telecommunication supply pipelines. Due to 5,2 breaks in the distribution mains and 22, in service and in-house piping, gas supply was disrupted for.86 million customers [1]. Many pipelines built with the latest earthquake-resistant technologies such as welded steel pipelines, however, were not severely damaged even though such strong seismic motions or PGD had not been incorporated into conventional earthquake-resistant design guidelines. Therefore, even though we have to consider the effects of such strong motions and/or PGD, rational earthquake-resistant design and maintenance can be achieved, and the methods to achieve such design are partly described in the new design guidelines for gas transmission pipelines that were revised recently [2, 3]. This paper summarizes the intensive studies that Tokyo Gas has been conducting for rational seismic design and maintenance of buried pipelines [4-19]. The final goal of the studies is to achieve Site-specific Design and Maintenance (SSDM) by eliminating conservatism through precise evaluation methods of pipeline deformation subjected to seismic motions or PGD using detailed available information on the pipelines and the circumstances. The studies include four essential technologies for evaluation of earthquake-resistance of buried pipelines: (1) Ground movement due to seismic motion and PGD, (2) Soil-pipeline interaction, (3) Deformability of pipelines, and (4) Evaluation method for pipeline deformation. Experimental and analytical studies by Tokyo Gas for each technology are described in the paper. 2. NEW CONCEPTS OF EARTHQUAKE-RESISTANCT DESIGN FOR GAS TRANSMISSION PIPELINES The strong seismic motion and the subsequent PGD observed during the 1995 Hyogoken-nanbu earthquake were not incorporated into the conventional earthquake-resistant design guidelines for many structures; therefore, Japan Society of Civil Engineers (JSCE) issued three phases of Proposal on Earthquake Resistance for Civil Engineering Structures in 1995 [2], 1996 [21] and 2 [22]. The proposal adopted the following two concepts:
Level of seismic motion Level 1 Level 2 Probability and magnitude of earthquake General seismic motion which occurs once or twice during the lifetime of the pipeline Very strong seismic motion due to inland or trench types of earthquake likely to occur at a low probability during the lifetime of the pipeline Definition of seismic motion for design Velocity response spectrum per unit seismic coefficient determined by taking envelope of velocity spectra converted from acceleration spectra, which were obtained from analysis of seismic waves during past earthquakes based on quantification theory Design seismic motion I determined for inland type of earthquake by obtaining the velocity response spectrum on the seismic base rock at the hypocenter region and nearby sites during the Hyogoken-Nanbu Earthquake, considering the non-excess probability Design seismic motion II determined for trench type of earthquake by observation during past earthquakes Design seismic motion IIIdetermined for Required performance of pipeline No severe deformation and no repair Large deformation but no gas leakage inland type of earthquake by fault analysis Table 1 Seismic motion and required performance of gas transmission pipelines specified in Recommended Practice for Design of Gas Transmission Pipelines [2, 15] (a) Two types of earthquake motions should be considered in assessing the aseismic capacity of civil engineering structures. The first type (referred as Level 1 earthquake motion, hereafter) is likely to strike a structure once or twice while it is in service. The second type ( Level 2 earthquake motion ) is very unlikely to strike a structure during its lifetime, but when it does, it is extremely strong. The level 2 earthquake motion includes those generated by interplate earthquakes in the ocean and those generated by earthquakes by inland faults. (b) The expected aseismic performance of civil engineering structures should be determined considering the degree of importance of the structures and the likelihood of the earthquake motion. The degree of importance of the structures can be determined based on factors such as (i) the effect of structural damage on life and survival, (ii) the effect of structural damage on evacuation, relief and rescue operations, and (iii) the effect of structural damage on everyday functions and economic activities. The above concepts were also adopted by the Basic Disaster Management Plan [23], which was revised in July 1995 by the Central Disaster Management Council. To reflect the concepts that were proposed by JSCE and specified by the government, the Japan Gas Association (hereafter, referred as JGA ) revised the seismic design guidelines, Recommended Practice for Design of Gas Transmission Pipelines (hereafter, the JGA Guidelines against seismic motions ) in 2 [2]. Both Level 1 and Level 2 seismic motions are considered in the design. Table 1 summarizes the definition of the motions and the performance required for gas transmission pipelines at each level of seismic motion [15]. In addition to the establishment of the guideline against strong earthquake motions, JGA established Recommended Practice for Design of Gas Transmission Pipelines in Areas Subject to Liquefaction (hereafter, the JGA Guidelines against liquefaction ) in 22 [3] for design of gas transmission pipelines subjected to PGD due to ground liquefaction during earthquakes. Figure 1 shows the design procedure of the evaluation of earthquake-resistance of buried gas transmission pipelines against liquefaction.
Design of pipeline (location, geometry, material, etc.) Identification of area where design against liquefaction is required Estimation of liquefaction-induced ground displacement Soil-pipe interaction Analysis of pipeline deformation Pipeline deformability Evaluation of earthquake-resistance Figure 1 Procedure of evaluation of earthquake-resistance of buried gas transmission pipelines subjected to liquefaction [3, 15] According to the concepts of the above new guidelines, Tokyo Gas has been conducting intensive and inclusive studies for rational seismic design and maintenance of buried pipelines, which are described in the following sections. 3. STUDIES ON ESSENTIAL TECHNOLOGIES 3.1 Ground Movement During Earthquakes For seismic motion, both Level 1 and Level 2 earthquake motions are considered in the JGA Guidelines against seismic motions [2]. The Level 2 earthquake motion is specified as a velocity response spectrum with a maximum velocity of.1 m/s, which was determined considering 16 seismic motions recorded near the hypocenter region during the 1995 Hyogoken-Nanbu earthquake and a non-excess probability of 9 % to avoid conservatism. In the case of irregular surface layers, ground strain caused by inclined seismic base rock could be larger than that of uniform ground. Analytical investigation was conducted with various geometric and geotechnical parameters such as degree of base rock inclination, shear wave velocity and thickness of the surface layers, pipeline diameters and seismic motions [8, 9]. The analytical results plotted in Figure 2 show that the maximum ground strain due to the inclination of the base rock is.3 % in the presence of the strong seismic motions observed in the 1995 Hyogoken-nanbu earthquake. The results were also reflected in the revised JGA Guidelines against seismic motions [2].
Maximum ground strain (%).6%.3%.% Kobe Port Island (N-S) Higashi-Kobe Bridge (N-S) Kobe University (N-S) 3 6 9 Inclination of base rock (degree) Figure 2 Effect of base rock inclination on ground strain subjected to seismic motions [8, 9] Ground displacement occurring as PGD is also specified in the JGA Guidelines against liquefaction [3]. Design to withstand liquefaction is required at the background of quaywalls whose height is greater than or equal to 5 m or slopes whose gradient is greater than or equal to 1 %. The horizontal displacement was set according to the data observed in the 1964 Niigata, the 1983 Nihonkai-chubu and the 1995 Hyogoken-nanbu earthquakes [24] with an adequate design margin, and the maximum displacement of 3 m was also adopted due to the fact that 95 % of the horizontal displacement greater than 1 m was less than 3 m during the Niigata and the Nihonkai-chubu earthquakes [3]. Rational design or maintenance of pipelines could be achieved as well by evaluating the characteristics of the ground in the Tokyo area [17]. 3.2 Soil-Pipeline Interaction Soil-pipeline interaction determines the external forces on buried pipelines from the adjacent ground when the input due to seismic motions or PGD is determined. Soil-pipeline interaction in the axial direction was investigated by conducting full-scale experiments using a 3-D shaking table. The 3-D shaking table, measuring 4 m by 4 m, has a capacity of 196 kn for load,.5 m for displacement, 1.5 m/sec for velocity and 1.1 times the gravity for acceleration. Figure 3 (a) shows the experimental setup of the experiment investigating the soil-pipeline interaction in the axial direction for a 6-mm diameter pipe. The experimental result shown in Figure 3 (b) indicates that the soil-pipe interaction in the axial direction showed a significant reduction after a few cycles of the displacement. Inclusive experiments that Tokyo Gas conducted showed the same trend [6], which can be used for rational maintenance of the existing pipelines. Full-scale tests using the shaking table and dynamic direct shear tests showed that the velocity due to strong seismic motions had little effect on the soil-pipe interaction in the axial direction [6], which made a significant contribution to the revision of the JGA Guidelines against seismic motions [2]. Soil-pipe interaction in the transverse horizontal direction of pipelines was also investigated by conducting full-scale experiments for pipelines with various diameters, cover depths, and surrounding soils [5]. The experimental results showed that the peak value of the soil-pipe interaction in the transverse horizontal direction had good agreement with the recommendations in the ASCE (American Society of Civil Engineers) guidelines [25], which were proposed by Trautmann and O Rourke [26].
Sand box Pipe Soil-pipe interaction in axial direction (kpa) Shaking -15-1 -5 5 1 15 Relative displacement (mm) table (a) Experimental setup (b) Experimental results (.75 m/sec) Figure 3 Full-scale experiment on soil-pipe interaction in the axial direction using a 3-D shaking table 4 2-2 -4 1 2 A 3-D analytical model for soil-pipe interaction was also developed to evaluate soil-pipe interaction in various subsurface conditions for rational design and maintenance. The model, called the 3D Nor-Sand model was developed by collaboration with Cambridge University in the UK through an international collaborative project with Advantica (UK), Gaz de France (France), Italgas (Italy), TransCanada Pipelines (Canada) and the Geological Survey of Canada (Canada). The Nor-Sand model, originally developed by Jefferies [27], was implemented into ABAQUS for 3-D analyses by Dasari and Soga [11]. The model attempts to reproduce accurately the dilation and softening on the dry side of the critical state and assumes that there is a unique critical state line. Figure 4 shows the soil-pipe interaction in the transverse horizontal direction when the embedment ratio H/D, which is cover depth divided by pipe diameter, is 11.5 for both the experiment conducted by Trautmann and O Rourke [26] and the analytical simulation using the developed model [19]. Good agreement was observed between the experimental and analytical results in the soil-pipe interaction not only for the peak value but also the gradual reduction in the value when the displacement is large. Using the developed model, soil-pipe interaction in transverse horizontal and transverse vertical directions for deep embedment conditions was also evaluated [19]. Large embankments, which have been constructed along large rivers in Tokyo, could induce significant ground settlement and affect the pipeline buried under the rivers. The embedment ratio H/D for these situations can be as large as 4 to 8, which is well beyond the range of the recommendations given by the ASCE guidelines [25] as well as of the experimental results reported. Figure 5 (a) shows the comparison between the extrapolation of ASCE recommendations and the analytical results using the developed model. Using the analytical results, the conservatism in the soil-pipe interaction in both transverse horizontal and vertical can be removed, as shown in Figure 5 (b). In the same way, rational design and maintenance can be achieved by using the developed analytical model without losing the margin for safety if detailed subsurface information is available at the specific sites.
6 Force (kn/m length) 4 2 Analysis Experiment 2 4 6 8 Displacement (mm) Figure 4 Analytical results on soil-pipe interaction in the transverse horizontal direction [19] Peak dimensionless force, Nq 5 4 3 2 1 Analysis (Nor-Sand) ASCE 2 4 6 8 Embedment ratio, H/D (a) Comparison between extrapolation of ASCE recommendation and analytical results Peak dimensionless force, Nqc 4 3 2 1 Horizontal: 35 degree Horizontal: 4 degree Horizontal: 45 degree Vertical: 35 degree Vertical: 4 degree Vertical: 45 degree 1 2 3 4 H/D (b) Proposed design chart for soil-pipe interaction in the transverse horizontal and vertical directions Figure 5 Analytical results using the 3-D Nor-Sand model [19]
Displacement meter Load Cell 3.1m 2m A A Hydraulic jack 65-mm-diameter pipe 1-mm-diameter pipe Hydraulic jack (a) Plan view 1m Load Cell.9m 1.56m.75m.6m (b) Side view (Normal backfill) 2.58m (c) Side view (EPS backfill) Figure 6 Experimental setup for evaluation of EPS backfill effect on soil-pipe interaction [16] (a) Slip surface (Normal backfill) (b) Slip surface (EPS backfill) Figure 7 Slip surfaces at the section A-A after the tests [16] Normalized force per unit projected area 1.2 1.8.6.4.2 Test 1(Normal backfill) Test 2 (Normal backfill) Test 3(EPS backfill) 5 1 15 Displacement (mm) Figure 8 Experimental results of EPS backfill effect on soil-pipe interaction [16]
For the pipelines constructed in areas where such PGD is expected, the pipe stiffness should be increased with a larger diameter, thickness or strength, or the soil-pipe interaction should be reduced. The effect of EPS (Expanded Poly-Styrene) for backfill on reduction of soil-pipeline interaction was evaluated for earthquake-resistant design by conducting full-scale experiments [16]. A 1-mm diameter pipeline was buried in the ground, and pushed into the ground horizontally with a hydraulic jack for 3 mm, and the reaction force was measured to evaluate the soil-pipe interaction in the transverse horizontal direction. Figure 6 (a) shows a plan view of the experimental setup. Two kinds of tests were conducted: Tests 1 and 2 were performed with backfill of compacted sand only, and EPS backfill was used for Test 3. Side views of both kinds of the tests are shown in Figures 6 (b) and (c), respectively. Figure 7 (a) shows the plane of soil slip observed at the Section A-A, which is shown in Figure 6 (a), by removing half of the sand in the test compartment after Test 1. On the other hand, for Tests 2 and 3, the plane of soil slip reached the EPS block, and then the slip occurred between the EPS and sand, as shown in Figure 7 (b). Figure 8 shows the experimental results: normalized force per unit projected area vs. relative displacement of pipe in the ground. Here, the normalized force per unit projected area was calculated from the force per unit projected area, which was adjusted so that the internal friction angles of the three tests are equal and normalized with the average of the maximum values recorded during Tests 1 and 2. The results showed that the EPS backfill had a significant effect on reducing the soil-pipe interaction. In the case where EPS was used for backfill, the peak value of the measured reaction force was approximately half of that in the case where compacted sand was used for backfill. 3.3 Pipe Deformability Pipe deformability is a key aspect taking full advantage of the lessons learned from the 1995 Hyogoken-nanbu earthquake for rational earthquake-resistant design and maintenance. Because bends represent locations of local restraint with respect to flexural and axial deformation of buried pipelines as shown in Figure 9 (a), most of the damage to steel pipelines in the previous major earthquakes was concentrated at the bends [1, 28]. Therefore, full-scale bending experiments were conducted for various bends including low-angle elbows and cold bends in addition to straight pipes to evaluate the full ductility and deformability of welded steel pipelines [4, 7, 1, 12, 14]. Figure 1 (a) shows the deformation of a 3-mm diameter elbow with 9 degrees of initial bend angle when the change in bend angle was 81 degrees in the closing mode [7]. Figure 1 (b) shows the deformation of a 4-mm diameter cold bend with approximately 1 degree of initial bend angle when the change in bend angle was 135 degrees in the closing mode [1]. In both cases, no gas leakage was observed due to high ductility and deformability of the steel pipe bends. Analyses with the Finite Element Method (FEM) using shell elements were also conducted to evaluate quantitatively the deformation behavior of the pipes under a high level of strain. Figures 11 (a) and (b) compare the analytical results with experimental ones for 3-mm elbows with 45 degrees of initial bend angle when the change in bend angle was 11 degrees in the closing mode. Good agreement between experimental and analytical results was observed for the strain distribution around the central cross section in both the circumferential and longitudinal directions.
Buried Pipeline Elbow Permanent Ground Deformation (PGD) Figure 9 PGD effect on buried pipelines with elbows (a) 3-mm diameter elbow (b) 4-mm diameter cold bend (JIS-STPT37, closing mode) [7] (API 5L X6, closing mode) [1] Strain, ε (%) 8 4-4 Figure 1 Bending experiments on pipe bends Experiment (External surface) FE analysis (External surface) FE analysis (Internal surface) Strain, ε (%) 8 4-4 Experiment (External surface) FE analysis (External surface) FE analysis (Internal surface) -8-8 -18-9 9 18-18 -9 9 18 Angle, φ (degree) Angle, φ (degree) (a) Circumferential direction (b) Longitudinal direction Figure 11 Strain distribution at the central cross-section of a 3-mm diameter elbow with 45 degrees of initial bend angle in the closing mode [12] 3.5 Evaluation of Pipeline Deformation Evaluation method of pipeline deformation can be effective when the above three technologies are well established. A new modeling technique, called the HYBRID model, was developed to evaluate the deformation behavior of large-scale buried pipelines subjected to PGD, using shell elements for the portions where large, localized strains occur and beam elements where a relatively small deformation is expected. Continuity between the shell and beam elements is achieved with multipoint constraints. Soil-pipeline interactions are modeled with non-linear spring elements, which were allocated at the top and bottom of the pipeline in the axial, transverse vertical and horizontal directions. [4, 7, 12].
Beam element Beam element 4 x diameter Shell element Multipoint Constraint Shell element 4 m 4 m Spring element for stresses conveyed to pipeline from adjacent ground (a) Analytical model around elbow (b) Modeling for connection between shell elements and beam elements Figure 12 HYBRID model used for analyses of buried pipelines [4, 7, 12] C E D A F (b) Before experiment Movable box A Fixed box B 1-mm-diameter pipe Short leg C Long leg D 9-degree elbow E Pulley system F B 2m (a) Plan view of experimental setup (c) After experiment Figure 13 Experiments on large deformation behavior of buried pipelines with bends subjected to PGD [18] Distance from the long leg (m) -6 Experiment FEA Original position Short leg Long leg Elbow 2-1 -8-6 -4-2 2 Distance from the short leg (m) -4-2 Strain, (%) 4 2-2 Elbow max. measured strain Experiment (extrados) Experiment (intrados) FEA (extrados) FEA (intrados) Lp 5 1 15 Distance from the short leg edge, Lp (m) (a) Deformation of the pipeline after the test (b) Distribution of axial strain in the longitudinal direction Figure 14 Comparison between analytical and experimental results [18]
Laboratory full-scale experiments of PGD effects on steel pipelines with elbows were conducted to refine and validate the analytical model so that complex soil-pipeline interactions can be numerically simulated with the precision and reliability necessary for planning and design [18]. Figure 13 (a) shows a plan view of the experimental setup. The test compartment was composed of a movable box (A) and a fixed box (B) within which the instrumented 1-mm diameter pipeline was installed and backfilled so that the embedment ratio, H/D, should be 8.5. The L-shaped moveable box, which had inside dimensions of 4.2 m by 6 m by 1.5 m deep, was displaced by a pulley-loading system (F). The fixed box, which was anchored to the floor, was designed to simulate stable ground adjacent to a zone of PGD similar to that illustrated in Figure 9. Approximately 6 tons of Cornell Sand, which is a clean sand (approximately 3% by weight of fines), was used for each experiment. Figures 13 (b) and (c) show the ground surface of the test compartment before and after the test. Surficial heaving and depression could be seen in the area near the pipeline elbow and the abrupt displacement plane between the movable and fixed boxes after the test. Figure 14 (a) compares the deformed pipeline shape of the analytical model with the measured deformation of the experimental pipeline. Figure 14 (b) shows the measured and predicted longitudinal strains under maximum ground deformation on both the extrados and intrados surfaces along the pipeline. Overall, there is good agreement for both the magnitude and distribution of measured and analytical strains and deformation, and the analytical model was able to simulate the observed performance in a reliable way. The analytical model was also adopted in the revised JGA Guidelines against liquefaction [3]. 6. CONCLUSIONS For design and maintenance of pipelines against strong seismic motions and subsequent PGD, Tokyo Gas has been conducting intensive and inclusive studies in the four essential technologies: (1) Ground movement due to seismic motion and PGD, (2) Soil-pipeline interaction, (3) Deformability of pipelines, and (4) Evaluation method for pipeline deformation. This paper summarizes some of the studies, such as analytical investigation of the effect of base rock inclination on ground strain due to strong seismic motions, experiments using a 3-D shaking table and development of a new analytical model of soil-pipe interaction, bending experiments and analyses of welded steel pipes on deformability, and analytical model of pipeline deformation under PGD with full-scale experiments for validation and calibration. Part of the studies made a significant contribution to the revision of the new JGA guidelines against strong seismic motions and PGD due to ground liquefaction. By using the results of the studies and conducting further investigation on precise evaluation of the earthquake-resistance of pipelines at specific sites, Tokyo Gas is achieving rational design and maintenance of gas pipelines without losing the margin for safety. ACKNOWLEDGEMENTS: The authors wish to thank Professor Thomas D. O Rourke of Cornell University, Professor Masanori Hamada of Waseda University, Ikuo Towhata of Tokyo University, and Professor Susumu Yasuda of Tokyo Denki University for their suggestions, and also Dr. Kenichi Soga of Cambridge University, Dr. Siam Yimsiri of Burapha University, Dr. Ganeswara Rao Dasari of the National University of Singapore, who led to significant improvements in this research. Thanks are extended Dr. P. C. F. Ng of Advantica, Dr. I. Konuk of the Geological Survey of Canada, Dr. M. Zarea of Gaz de Grance, Dr. M. Piovano of Italgas and Mr. A. Trigg of TCPL for their advice on soil-pipeline interaction modeling, and Messrs. Takehiko Suzuki and Yasuyuki Takahashi of Kanpai Co., Ltd., for their assistance in conducting the experiments. Special thanks go to Messrs. Takashi Kobayashi, Kazunori Shimamura, Noritake Oguchi, Yoshihisa Shimizu, Tomoki Masuda, Takahito Watanabe,
Hirokazu Ando, Hiroshi Sugawara, Mio Kobayashi, Kenichi Koganemaru, Hiroshi Yatabe, Naoyuki Hosokawa, Masato Nakayama and Daisuke Ujiie of Tokyo Gas Co., Ltd., for their invaluable advice. REFERENCES 1. Oka, S. (1996). Damage of Gas Facilities by Great Hanshin Earthquake and Restoration Process, Proceedings, 6th Japan-U.S. Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermeasures Against Soil Liquefaction, NCEER-96-12, MCEER, Buffalo, NY, 111-124. 2. Japan Gas Association (2). Recommended Practice for Earthquake Resistant Design of High Pressure Gas Pipelines, Japan Gas Association (in Japanese), Tokyo, Japan. 3. Japan Gas Association (22). Recommended Practice for Earthquake Resistant Design of Gas Transmission Pipelines against Ground Liquefaction, Japan Gas Association (in Japanese), Tokyo, Japan. 4. Yoshizaki, K. and Oguchi, N. (1996). Estimation of the deformation behavior of elbows for an earthquake-resistant design, Proceedings, 11th World Conference on Earthquake Engineering, Acapulco, Mexico, Paper No. 1783, Elsevier Science. 5. Ando, H., and Kobayashi, M. (1996). Nonlinear Characteristics of Ground Constraint on Buried Pipes Caused by Lateral Displacement during Earthquakes, Proceedings, 11th World Conference on Earthquake Engineering, Paper No. 1596, Elsevier Science. 6. Kobayashi, M., Ando, H. and Oguchi, N. (1998). Effects of Velocity and Cyclic Displacement of Subsoil on its Axial Restraint Force Acting on Polyethylene Coated Steel Pipes During Earthquakes, Journal of Structural Mechanics and Earthquake Engineering (in Japanese), No. 1, No. 591/I-43, 299-312. 7. Yoshizaki, K., Hosokawa, N., Ando, H., Oguchi, N., Sogabe, K. and Hamada, M. (1999) Deformation behavior of buried pipelines with elbows subjected to large ground deformation, Journal of Structural Mechanics and Earthquake Engineering (in Japanese), JSCE, No. 626/I-48, 173-184. 8. Kobayashi, M., Hosokawa, N. and Watanabe, T. (1999). Earthquake Resistant Countermeasures for Pipelines in Tokyo Gas F. T. R. L., Proceedings, World Gas Conference, Niece. 9. Kobayashi, M., Ando, H. and Watanabe, T. (2). Amplification of Ground Strain in Irregular Surface Layers During Strong Ground Motion, Proceedings, 12 th World Conference on Earthquake Engineering, No. 1433, New Zealand. 1. Yatabe, H. and Watanabe, T. (2). Effects of Cold Working on Bending Deformation Behavior of Steel Gas Pipeline, Proceedings, 4 th Japan Conference on Structural Safety and Reliability (in Japanese), 89-B, 537-54. 11. Dasari, G. R. and Soga, K. (2) Numerical analysis of sand lateral load tests, Report to Tokyo Gas, Cambridge University (unpublished). 12. Yoshizaki, K., O Rourke, T. D. and Hamada, M. (21). Large Deformation Behavior of Buried Pipelines with Low-angle Elbows Subjected to Permanent Ground Deformation, Journal of Structural Mechanics and Earthquake Engineering, JSCE, Vol. 18, No. 1, No. 675/I-55, 41-52. 13. Kobayashi, T., Shimamura, K., Oguchi, N., Ogawa, Y., Uchida, T., Kojima, S., Kitano, T. and Tamamoto, K. (21). Recommended Practice for Design of Gas Transmission Pipelines in Areas Subject to Liquefaction, Proceedings, International Gas Research Conference, TP-34, Amsterdam. 14. Fukuda, N., Yatabe, H., Masuda, T. and Toyoda, M. (22). Effect of Changes in Tensile Properties due to Cold Bending on Large Deformation Behavior of High-Grade Cold Bend Pipe, Proceedings, 4 th International Pipeline Conference, IPC22-27129, 363-37. 15. Masuda, T., Kobayashi, T., Yoshizaki, K. and Kobayashi, M. (22). Recommended Practice for
Design of Gas Transmission Pipelines in Areas Subject to Liquefaction, Proceedings, International Pipe Dreamer s Conference, Yokohama, Japan, 589-599. 16. Yoshizaki, K. and Sakanoue, T. (22). Earthquake-Resistant Design for Pipelines Subjected to Permanent Ground Deformation using EPS Backfill, Proceedings, 8 th U.S.-Japan Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermeasures against Liquefaction, II-2. 17. Yasuda, S., Shimizu, Y., Koganemaru, K., Isoyama, R., Ishida, E. and Matsumoto, K. (22). Estimation of the Zones Susceptible to Liquefaction-induced Flow in Tokyo, Proceedings, 8 th U.S.-Japan Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermeasures against Liquefaction, III-6. 18. Yoshizaki, K., O Rourke, T. D. and Hamada, M. (23). Large Scale Experiments of Buried Steel Pipelines with Elbows Subjected to Permanent Ground Deformation, Journal of Structural Mechanics and Earthquake Engineering, JSCE, Vol. 2, No. 1, No. 724/I-62, 1-11. 19. Yimsiri, S., Soga, K., Yoshizaki, K., Dasari, G. R. and O Rourke, T. D. (23) Lateral and Upward Soil-Pipeline Interaction in Sand for Deep Embedment Conditions, submitted to Journal of Geotechnical and Geoenviromental Engineering, ASCE, Reston, VA. 2. Japan Society of Civil Engineers (1995) First Proposal on Earthquake Resistance for Civil Engineering Structures. 21. Japan Society of Civil Engineers (1996) Second Proposal on Earthquake Resistance for Civil Engineering Structures. 22. Japan Society of Civil Engineers (2) Third Proposal on Earthquake Resistance for Civil Engineering Structures. 23. Central Disaster Management Council (1995) The Basic Disaster Management Plan. 24. Hamada, M. and Wakamatsu, K. (1998) A Study on Ground Displacement Caused by Soil Liquefaction, Journal of Geotechnical Engineering, JSCE, No. 596/III-43,, 189-28. 25. American Society of Civil Engineers (1984). Guidelines for the Seismic Design of Oil and Gas Pipeline Systems, Committee on Gas and liquid Fuel Lifelines, Technical Council on Lifeline Earthquake Engineering, ASCE, New York. 26. Trautmann, C. H. and O Rourke, T.D. (1985) Lateral Force- Displacement Response of Buried Pipe, Journal of Geotechnical Engineering, ASCE, Reston, VA, Vol.111, No.9, 177-192. 27. Jefferies, M. G. (1993) Nor-Sand: a simple critical state model for sand, Geotechnique, 43, No. 1, 91-13. 28. Japan Gas Association (1984), Nihonkai-Chubu Earthquake and Gas Facilities (in Japanese), Japan Gas Association, Tokyo Japan, 28-79.