The Tenth International Symposium on Mitigation of Geo-disasters in Asia Matsue Symposium Place: Shimane Civil Center, Matsue Date: 8 October 2012This study is focusing on behavior of ductile iron pipelines with the earthquake resistant joint buried across a fault being used widely for water pipelines in Japan. It is necessary to design a pipeline carefully in case of crossing a fault, because the partially large displacement occurs on the pipelines when a fault moves by an earthquake. However, there are few studies on behavior of ductile iron pipelines. We analyzed the behavior of pipelines near a fault by large displacement analysis method, and we confirmed that the earthquake resistant joint nearest to a fault began to move when a fault began to move, then the joints next in line began to move when the joints movement reached their capacity. In this study, we investigated the behavior of ductile iron pipeline installed into a sand container which moved like a fault for verification of pipeline behavior analysis. As a result, we confirmed that pipeline showed the behavior like the analysis result and we verified the validity

Erami, M. H

Kaneko, Shogo

Miyajima, Masakatsu

Kyoto University Research Information Repository

Title Study on Behavior of Ductile Iron Pipelines with EarthquakeResistant Joint Buried across a FaultAuthor(s)Kaneko, Shogo; Miyajima, Masakatsu; Erami, M. HCitationMatsue Conference Proceedings (The Tenth InternationalSymposium on Mitigation of Geo-disasters in Asia = 第10回地震・地盤災害軽減に関するアジア会議及び現地討論会)(2012): 151-156Issue Date2012-10-08URL http://hdl.handle.net/2433/180402RightType PresentationTextversionpublisherKyoto UniversityStudy on Behavior of Ductile Iron Pipelines with Earthquake Resistant Joint Buried across a Fault  Shogo Kaneko (Ductile Iron Pipe R & D Dept, Kubota Corporation, Japan) ・ Masakatsu Miyajima (School of Environmental Design, Kanazawa University, Japan) ・ M. H. Erami (Graduate School of Natural Science and Technology, Kanazawa University, Japan)   Abstract. This study is focusing on behavior of ductile iron pipelines with the earthquake resistant joint buried across a fault being used widely for water pipelines in Japan. It is necessary to design a pipeline carefully in case of crossing a fault, because the partially large displacement occurs on the pipelines when a fault moves by an earthquake. However, there are few studies on behavior of ductile iron pipelines. We analyzed the behavior of pipelines near a fault by large displacement analysis method, and we confirmed that the earthquake resistant joint nearest to a fault began to move when a fault began to move, then the joints next in line began to move when the joints movement reached their capacity. In this study, we investigated the behavior of ductile iron pipeline installed into a sand container which moved like a fault for verification of pipeline behavior analysis. As a result, we confirmed that pipeline showed the behavior like the analysis result and we verified the validity.  Keywords. ductile iron pipe, earthquake, earthquake resistant joint, fault, pipeline behavior   1. Introduction In a fault caused by inland earthquake, the magnitude of slippage may be as much as several meters, and structures existing near ground surface may suffer a great deal of localized damage, if a large crack appears near the ground surface. Because of this possibility, the pipelines across a fault must be designed carefully. However, very few researches study how ductile iron pipelines distributed across a fault behaves in response to fault movements; a design method has not been established. This paper reports on these. (1) Simulation analysis of behavior of ductile iron pipelines buried across a fault (2) Verification of analysis results with experiment (3) Assessment of the safety of pipeline  2. Simulation analysis of pipeline behavior 2.1 Analysis method In displacement analysis for buried pipelines, a behavior analysis method is generally used in which pipes are expressed as beams laid on an elastic floor, and their joints and the interactions with the ground as springs (Fig.1). In the conventional method, the directions of springs that link pipe and ground are fixed. So, when the ground displacement in the fault reaches several meters, drastic errors in analysis may result. Therefore, in this study, we employed large-displacement analysis method which the directions of the springs can change depending on the movements of pipe and ground. The method used in this study is shown in Fig.2.           Fig. 1 Outline of analysis model              Fig. 2 Large-displacement analysis method  継手ばね地盤ばね管Pipe Joint SpringsGroundSpringsPipeline before movementPipeline aftermovementGround springs1512.2 Analysis model The analysis model is shown in Fig.3. A reverse fault model, in which horizontal displacement was 2.0 m, vertical displacement was 1.1m and inclination was 29 degrees, was set up with reference to the result of a survey by Kataoka et al. of the Nojima fault, which underwent in the Kobe Earthquake. In this study, the length of each pipe was set at 1.7 meters, a value smaller than the regular pipe length 5m, so that the behavior of multiple pipes in this displacement range could be analyzed. The pipeline was modeled as an assembly of beams connected with joint springs and ground springs. Considering the properties of the elements in this model, these springs were assumed to be non-linear springs. The properties of the joint springs were determined based on results of experimental studies. For instance, the rotation spring of joint becomes resistant to further deflection when its deflection angle reaches 5.3 degrees, the limit value of deflection (Fig.4). The ground spring property was based on friction between pipe and ground and the reactive force from the ground. For instance, the relationship between friction in a direction orthogonal to the axis and displacement in that direction were set up as bilinear relationships (Fig.5).                     Fig. 3 Analysis model and conditions               Fig. 4 Joint spring (rotation)                Fig. 5 Ground spring (orthogonal direction)  2.3 Analysis result (1)Pipeline behavior Results for analysis of pipeline behavior near the fault are shown in Fig.6. The pipeline could follow fault displacement because of deflections in the joints A, B, A’ and B’. The displacement in the Y-direction at joints B’ and C’ was almost the same as the 1.1 m displacement of the ground, indicating that they moved together with the ground.            Fig. 6 Analysis result of pipeline behavior  2.0m400m1.1ｍ29°0.85m1.7m jointFault planepipeline（DN250 NS-type)Fault crossing pointFault displacementCoefficient of subgrade reaction K = 20700 (kN/m3)Fault type Reverse faultAmount of faultdisplacement2.3mPipeline DN250 NS-type ductile iron pipePipeline length 400mBurial depth 0.6mGround conditionCoefficient of subgrade reactionK=20700(kN/m3)θa=5.3°Joint deflection angle θKraBending moment MKrbOrthogonal direction frictionKt1δt1Kt2displacementFault planeB’A’ABB AA’B’CCC’XY(m)0 1 2 3 4 5C’C B A A' B' C'X 0.82 0.87 0.95 1.10 1.17 1.23 2.00Y 0.00 0.00 0.32 0.86 1.13 1.10 1.10GroundDisplacement(m)Joint152(2)Joint contraction/expansion Shown in Fig.7 is the analysis result for the contractions/expansions of the joints. Since the ground was displaced in such a way that the pipe had to contract in its axial direction, only contracting movements took place in the joints. In 37 joints centering on the fault, contraction was approximately 50 mm, the limit contraction value for each. The total contraction for the pipeline was 1.96 m, a value almost equal to the 2.0 m displacement of the ground in the axial direction, showing that the ground displacement was almost entirely absorbed by the joint contractions. The contractions of individual joints relative to the fault displacements (in the axial direction) are shown in Fig.8. Also shown is the movement of the pipe: when the fault displacement was still small, joint A, closest to the fault, contracted first. When the contraction in joint A reached its limit value, joint B began to contract; then, joint C, joint D and so on, one after another, following the movement of the joints closer to the fault.            Fig. 7 Joint contraction                  Fig. 8 Joint contraction  (3)Joint deflection angle The results of joint deflection angle analysis are shown in Fig.9. Plus or minus sign in front of deflection angles on the Y-axis indicates the direction of deflection. This graph shows that deflections were generated in 4 joints straddling the fault. Shown in Fig.10 are the deflections angles in Joints A, B and C relative to fault displacement orthogonal to the pipeline axis. Deflection was also first generated in joint A, the closest joint to the fault, when the fault began to move. When this deflection reached its limit value, joint B began to be deflected.                 Fig. 9 Joint deflection angle             Fig. 10 Joint deflection angle relative to fault displacement    -15-10-5051015Joint deflection angle (deg)ABCDA'B'C' D'Two-pairs of jointsstraddling a faultare deflectedJoint deflection angle (deg) +Joint-B’A’ABB AA’B’CCC’C’ D’ E’DFault plane-20246810120 0.2 0.4 0.6 0.8 1 1.2Fault displacement in orthogonal direction to pipe axis (m)Joint deflection angle (deg)Joint AJoint BJoint C系列4Fault displacement in orthogonal direction to pipe axis (m) Joint deflection angle (deg) 01020304050600 0.5 1 1.5 20102030405060Joint contraction (mm) 50mm contraction in 37 of 85 joints Joint contraction (mm) Fault displacement in pipe axial direction (m) A B C D E F G H I J K L M N O P Q R B’A’ABB AA’B’CCC’C’ D’ E’DFault plane1533. Verification experiment 3.1 Experiment method The validity of the analysis results of the pipeline behavior simulation was checked with a verification experiment in which actual pipes were used. As shown in Fig.11, we distributed DN75 NS-type ductile iron pipes in a sand container that was divided into two portions and filled with sand. One portion was then dropped 300 mm in the direction of 60 degrees to simulate a fault movement, and various measurements were taken on the pipeline.                 Fig. 11 Experiment method and conditions  3.2 Experiment result The setup of the experiment is shown in photo.1. Photo.2 shows the fault crossing part from the side and indicate fault. The experiment results of contractions of joint A and B relative to the fault displacements (in the axial direction) are shown in Fig.12. The analysis results are shown in this graph in addition, too. The pipelines moved following by the ground displacement, and it was confirmed that the experiment results were almost the same as the analysis results. We show the result of a measurement of pipeline behavior in fig.13. Like the analysis results, it was revealed that the pipeline followed fault displacement in the experiment results, too. However, in the joint A and A’, the closest joints to the fault, it turns out that the pipeline displacement magnitude in an experiment is smaller than analysis. Therefore I analyzed joint behavior in detail. The joint deflection angle of joint A, A’, B and B’ is shown in fig.14. With the container of the subsidence side, deflection angle of joint B’ neighboring joint A’ which was the closest to the fault was bigger. And we confirmed a tendency unlike the analysis result. In other words, it is estimated that the pipeline behavior of the fixed side is different from the subsidence side.              Photo 1 Setup of the experiment                  Photo 2 Fault part side             Fig. 12 Joint contractions  Pipes DN75 NS-typePipe length 1mNumber of joint 10Fault type Reverse faultSoil compacting 15 N-valueFault displacement-0.17m (X-direction)-0.30m (Y-direction)010203040500 50 100 150 200Fault displacement in pipe axial direction (m) Joint contraction (mm)   JointA   (experiment)   JointB   (experiment)   JointA   (analysis)   JointB   (analysis) ABCDEA’ B’ C’ D’ E’Fixed side Subsidence side0.3mXY154           Fig. 13 Pipeline behavior              Fig. 14 Joint deflection angle  3.3 Verification of ground spring In our analysis, we set the same ground condition in the fixed side and the subsidence side. We confirmed whether this was proper by an experiment. As shown in Fig. 15, as for the pipeline in the fixed side container, the ground reaction force acts from the upper part, as for the pipeline in the subsidence side container, it acts from the lower part. Therefore, as shown in Fig. 16, we installed DN75 ductile iron pipe in a sand container, and measured the ground reaction force when the pipe was displaced to above and down. The result is shown in Fig. 17. It turned out that the ground reaction force when the pipe moved downward was bigger than when it moved upward. From this experimental result, as shown in Fig. 17, we modeled ground spring and analyzed again. Joint deflection angle is shown in Fig.18. The analysis result which re-modeled the ground spring was approaching by the experimental result. We show the result of a measurement of pipeline behavior in fig.19 and the result of a measurement of deflection of joint A, B and C in fig.20.  (1)Only the joints near the fault behaved with fault movement. (2)When the fault began to move, the joints straddling the fault moved first. By the experiment result, the behavior of pipeline across a fault showed like the analysis result.       Fig. 15 Direction of ground reaction force           Fig. 16 Measurement method of ground reaction force               Fig. 17 Measurement result of ground reaction force            Fig. 18 Joint deflection angle -0.4-0.3-0.2-0.100.1-3 -2 -1 0 1 2 3X (m)Y (m)0246810-2 -1 0 1 2X (m)Joint contraction (mm) Fixed side Subsidence side △ Experiment ● Analysis  え Fault plane △ Experiment ● Analysis  え Fault plane BAA’ B’DN75 pipesandSand container0.6m051015202530350 5 10 15 20pipe displacement(mm)ground reaction force(kN)measurement (upward) measurement (downward) re-modeling (upward) re-modeling (downward) 0246810-2 -1 0 1 2X (m)joint deflection angle(degree)A B A’ B’ △ Experiment ● re-modeling  え B A A’ B’ 155           Fig. 19 Pipeline behavior             Fig. 20 Joint deflection angle relative to fault displacement  4. Conclusions We carried out a detailed pipeline behavior simulation and a verification experiment simulating distributed pipeline buried across a fault comprising ductile iron pipe with earthquake-resistant joints. As a result, the following conclusions were drawn. When the fault began to move, the joints straddling the fault moved first. When the deflection angles in these joints reached their maximums, the joints next in line began to move.  We intend to continue the simulation analysis under various conditions of fault and pipeline and ground, in order to establish a design method for ductile iron pipelines buried across a fault.   References Shojiro Kataoka et al. Oct. 2005. “Characteristics of Surface Fault Rupture Relating to Magnitude and Slip Type of Inland Earthquakes,” Journal of Japan Society of Civil Engineers No. 801/ I-73, pp 21 - 32Carreno R, Bonnard C (1997) Rock slide at Machupicchu, Peru. Landslide News 10:15–17. Japan Water Works Association. Mar. 1997. “Seismic Design and Construction Guidelines for Water Supply Facilities.”   S. Kaneko Ductile Iron Pipe R & D Dept, Kubota Corporation Amagasaki, Hyogo 660-0095, Japan e-mail: s-kaneko@kubota.co.jp  M. Miyajima School of Environmental Design, Kanazawa University Kanazawa, Ishikawa 920-1192, Japan e-mail: miyajima@t.kanazawa-u.ac.jp  M. H. Erami Graduate School of Natural Science and Technology, Kanazawa University Kanazawa, Ishikawa 920-1192, Japan e-mail: m_h_erami@yahoo.com  -8-6-4-2020 0.1 0.2 0.3 0.4Fault displacement in orthogonal direction to pipe axis (m)Joint deflection angle (deg)Joint AJoint BJoint C系列4Fault displacement in orthogonal direction to pipe axis (m) -0.4-0.3-0.2-0.100.1-3 -2 -1 0 1 2 3X(m)Y(m)experimentanalysis系列3Fixed side Subsidence side156

Study on Behavior of Ductile Iron Pipelines with Earthquake Resistant Joint Buried across a Fault

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Study on Behavior of Ductile Iron Pipelines with Earthquake Resistant Joint Buried across a Fault

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