Study On The Floating Reaction Of Buried Natural Gas Pipeline In Liquefaction Environment

Buried gas pipeline usually across a vast area, involves complex landform and geological type, inevitably through liquefaction zone. Soil liquefaction buoyancy makes underground pipelines go up, even exposed to ground surface and damaged, it is one of the main hazard zone of pipe in meizoseismal area. Establishing finite element model of pipeline floating reaction in liquefied area, analyzing the response of pipeline in liquefied soil to provide guidance for effective measures which can ensure the safe operation of pipelines. The main research contents and achievements are as follows:(1) Through literature research, this paper made research status analysis of pipeline floating reaction in liquefied area at home and abroad, summarized the methods and results of previous research employed in numerical analysis and experimental research.(2) Soil liquefaction mechanism, influence factors and liquefaction assessment method are studied, and analyzed the failure mechanism of pipeline in liquefaction zone to provide the theoretical foundation for the analysis of pipeline floating reaction in liquefied soil.(3) Based on the nonlinear finite element theory, established the nonlinear contact model between non-liquefied soil and pipeline, and soil spring model of liquefied soil zone and pipeline. According to actual operating environment of buried gas pipeline. Determining the boundary condition and effective calculation area of the model, and analyze pipeline floating reaction. The largest floating displacement occurs in the center of liquefaction zone. The junction of liquefaction zone and non-liquefaction zone a are dangerous positions.(4) Analyzing three kinds of factors for the pipeline floating reaction, included liquefaction characterization parameters, pipe sizes and materials, and operating construction conditions. The main factors of the pipe floating reaction are the length of the liquefaction zone, the thickness of the overlying the liquefied soil layer, pipe diameter, wall thickness, buried depth, temperature of the construction conditions, the pipeline operating pressure.(5) Based on the analysis of parameters affecting soil liquefaction reaction, using multivariate nonlinear regression theory, considering the main factors put forward simplified calculation formula of the maximum displacement and maximum axial strain.(6) Performing pipeline finite element simulation for liquefaction zone pipe that taken anti-floating measures. Making analysis of concrete buttress measures effect to weaken pipeline floating reaction, and putting forward reasonable scheme of concrete buttress size and arrangement.(7) Summarized some effective seismic measures applicable to buried gas pipeline in liquefaction zone. Designed monitoring and early warning construction scheme for pipeline floating reaction in liquefaction zone, which has function of liquefaction judgment, pipeline stress deformation analysis and early warning prompt function.