Research On The Analysis Method Of Fault Rupture Induced Response For Buried Pipelines Crossing The Reverse Fault

Damage of buried pipelines is primarily resulted from the surface rupture or near-surface rupture due to the fault movement. The response of buried pipelines crossing the fault is an important research content of lifelines earthquake engineering. Many of researchers have made much effort on this subject and proposed many analysis methods. Traditional analytic methods and numerical simulation methods which have been done are mainly to study the response resulted from the strike-slip fault. Because the effect of the reverse fault is very complex, the study on the response of the buried pipelines due to the reverse fault is difficult and less to be carried out. This thesis analyses the pipe segment which suffers the large deformation via the FEM model with shell element. And some preliminary results are obtained which can be referenced in the design of the buried pipelines crossing a reverse fault. The main work is as follows.1. Derive an equivalent compressive spring boundary to simplify the shell FEM analysis model and improve the artificial boundary method.2. Create a method to analyze the response of the pipeline due to the reverse fault movement. The pipe segment suffering large deformation is modeled with shell element and the soil spring is used around the pipe to consider the interaction between the pipe and the soil. Equivalent spring boundary and equivalent load boundary is introduced in the model to reduce the analysis time.3. On the basis of some examples centering on the main factors which influence the response of the pipeline crossing the reverse fault, this thesis discussed the failure mode of the pipe and obtained some preliminary results:(1) Crossing angle has small effect to the response of the buried pipeline under the action of the reverse fault. When the fault displacement is same, the maximum axial compressive strain of the buried pipeline with different crossing angle is very close.(2) The failure mode of the pipe with small diameter is much different from the pipe with large diameter. The failure part of the small diameter pipeline is at the intersection of the fault. And it needs a longer segment to be analyzed in order to reflect the stress and strain situation of the curved section at the passive wall. Along with the increase of the pipe diameter, the shell character of the pipe becomes more and more obvious and the failure segment becomes longer. Considered the analysis of the strain and the failure length of the pipeline, it would be helpful to the earthquake resistance to use the pipe with the diameter from 600mm to 1200mm in the cross- reverse fault pipeline design.(3) The pipe is damaged more seriously when the dip angle of the reverse fault is large. Under the same displacement of the fault, the larger dip angle, the larger strain of the pipe. It suggests that the pipe is sensitive to the vertical action.(4) The pipeline with greater depth would be damaged more seriously under the action of the reverse fault. While meeting the requirement of the minimum depth of the overlaying soil and the frozen depth, the cross-reverse fault pipeline is appropriate to be buried in shallow soil.