Shaking Table Test And Deformation Law Study Of Buried Pipeline Under Dynamic Dislocation Of Reverse Fault

The seismic performance and failure mechanism of buried pipelines crossing faults have always been the subject of continuous exploration by lifeline seismic engineering scholars.Since the 1971 San Fernando earthquake,scholars have used theoretical analysis,numerical simulation and soil-box test to study the seismic performance of buried pipelines,and have achieved rich scientific research results.At present,the research results that have been carried out are mainly to simulate fault dislocation by inputting linear static displacement,so as to explore the response law of buried pipeline crossing fault.However,the near fault strong motion observation results of many destructive earthquakes at home and abroad show that the fault dislocation is a dynamic process that changes with time.When an earthquake occurs,the transient maximum displacement of the fault often exceeds the permanent displacement obtained by geological survey after the earthquake,and the exceeding amplitude can reach more than 20%.In this paper,the high-density polyethylene(HDPE)water supply pipeline is taken as the research object.Through carrying out three groups of shaking table tests and corresponding finite element numerical model analysis,the seismic response of buried HDPE pipeline crossing reverse fault is studied,the force and deformation laws of the pipeline are summarized and analyzed,and the failure mechanism of buried pipeline under the action of dynamic dislocation of reverse fault is explored.The main contents of this paper are as follows:1.Based on the scientific investigation results after the 2023 Ms7.8 twin earthquake in Turkey,a 3-D analysis model of pipe-soil integrity under the action of fault dislocation is established,which reveals the seismic damage mechanism of buried water supply pipeline under the action of relatively large fault dislocation in Turkey Earthquake.The PE water supply pipeline with a diameter of 0.11 m was damaged in two places under the fault action of a horizontal displacement of 1.60 m and a vertical permanent displacement of 0.80 m.The model analysis showed that the distance between the failure points was 1.76 m,which was basically the same as the length of the pipeline repaired on site(about 1.80 m),which verified the reliability of the finite element model in this paper.2.Different from the experimental research that scholars have carried out to simulate the static process of fault dislocation by inputting linear displacement,the shaking table experimental design of the pipeline under the action of dynamic dislocation of thrust fault is completed in this paper,taking into account the boundary effect of the sidewall of the soil box and the influence of dynamic and static coupling.By selecting the vertical component of ground motion acceleration records near the thrust fault of the Chi Chi earthquake,and through baseline correction and amplitude adjustment,the displacement time history simulating the process of thrust dislocation is obtained,which is loaded as the input wave to the shaking table where the soil box is placed,and the other soil box is placed on the static ground next to the shaking table,so as to simulate the dynamic process of thrust dislocation.Three sets of shaking table tests of buried HDPE prototype water supply pipeline crossing reverse fault were designed and completed,and the influence of buried depth and wall thickness on the deformation response of buried pipeline was explored.3.The strain response of HDPE pipe under the action of reverse fault dynamic dislocation was measured in real time by shaking table test.The results show that the strain of the pipeline when the input wave reaches the peak displacement is significantly greater than that when the permanent displacement(platform section)occurs;With the increase of fault displacement,the strain response of the pipeline also increases.Under the action of dynamic dislocation of reverse fault,the deformation of buried pipeline on both sides of the fault is not completely symmetrical with respect to the fault plane,and the pipeline strain at the fault plane is not zero.4.In this paper,the similarity ratio is not considered,and the measured parameters of the pipe and soil for the experiment are directly input.The pipe-soil integral finite element model is used to simulate and analyze the shaking table test conditions.The results show that the strain of the pipeline when the transient displacement of the fault reaches the peak displacement is significantly greater than that of the last permanent displacement of the fault.Therefore,the pipeline anti fracture design based on permanent displacement of fault in the current seismic design code is not conservative.