The Analysis Of Buried Pipelines Under The Action Of Faults And The Study Of Seismic Methods

China is located between the circum-Pacific seismic belt and the Eurasian seismic belt, active faults widely distributed, long-distance oil and gas pipelines buried inevitably pass through earthquake fault zone. Robust and resilient steel tubes are generally able to withstand the test of the earthquake ground motion, but it is difficult to resist a larger permanent ground distancement faulting and ground damage arising. The study of the mechanical response behavior and parameters of buried pipeline under the action of fault slip, has of great significance for the seismic design and performance evaluation of the safety of the pipeline. The main work is as follows:(1) Making the research methods and anti seismic measures for the response of buried pipeline crossing fault at home and abroad, and the mechanical model used in the analysis of different methods is analyzed. In summarizing the research achievemnts and shortcomings of the previous theoretical analysis, numerical simulation and experimental method, and summing up the pipeline crossing fault seismic measures.(2) The fault mechanism and fault mode are studied, and the failure mode of buried pipeline under fault action is determined to be tensile and buckling failure. Analysis of the potential damage factors of pipeline failure, and establish the pipeline failure criterion.(3) The buried pipeline under the action of strike slip fault is the research object which conseders the material nonlinearity of the pipe and soil, the nonlinear geometrical deformation of the pipeline and nonlinear cantact between the pipe and soil, and establishing the finite element model of the pipe soil coupling, and to simulate the separation, closure and slip of the soil. Three line simplified model is chosen as the constrtutive equation of the pipe, and the ideal elastic-plastic constitutive model. The effective calculation length of the pipeline is 60m, and the effective calculation volume of the fault is 60m × 10m?× 8m. The shell MITC4 unit and the 8 node solid element are used respectively to discrete pipeline and fault soil, and the model is solved by using ADINA finite element software. Through the example calculation and analysis to verify the correctness and validity of the finite element model.(4) According to the finite element model of buried pipeline crossing fault, the mechanical response behavior of buried pipeline under fault is simulated, and the deformation state and potential failure position of pipeline are analyzed. Studying the influence of pipe size and material, the soil condition of the fault site and the operating condttion of the pipeline on the mechanical properties of pipeline. According to the influence law of parameters, pipe, soil cohesion, pipeline pressure and other factors on dimensionless, using the multiple linear and nonlinear regression theory, fitting out a simplified calculation formula for the strain of buried pipeline crossing the strike slip fault.(5) Establishing the finite element model of buried pipeline based on fluid structure interaction, and analyzing the response behavior of buried pipeline under the action of fault load and fluid. The influence of fluid parameters such as pressure, flow rate, temperature and density on the mechanical properties of pipeline is studied.(6) Based on the insufficients of 2 times Newmark-Hall tensile strain and soil spring finite element used to check the seismic resistance of pipeline of the seismic technical code for oil and gas transmission pipeline project(GB50407-2008), modifying the seismic design method of buried pipeline under fault, and improving the process of seismic design,and the measures for seismic retrofit of existing pipeline are put forward.(7) Design of safety monitoring and early warining system for buried pipeline crossing fault, it includes monitoring subsystem, data acquisition and transmission subsystem, data processing and analysis substem and early-warning subsystem in four parts. Forming the function of ground acceleration early warning, fault displacement early warning, pipeline strain early warning, pipeline leakage warning and so on, and proving the basis for the safe operation of the pipeline.