Dynamic Response Of Gas Pipelines Under Soil Landslide Based On SPH Method

With the development of environmental protection policies in various countries,the demand for natural gas as a clean energy source is increasing,and the construction of natural gas pipelines will also develop rapidly.By the end of 2016,China's natural gas pipeline mileage is about 68,000 kilometers.By 2020,the total length of China's natural gas pipeline construction is expected to reach 104,000 kilometers.Because of the complexity of natural gas pipeline passage and frequent geological hazards,especially landslide hazards,it is necessary to study the dynamic response of gas pipeline under landslide.At present,the numerical simulation of the gas pipeline under the soil landslide is generally driven by the force driven pipeline and the displacement load.Because the force of the soil on the pipeline is complicated during the landslide,the force driven and displacement loads are used to drive the pipeline.The difference between the shift and the actual process is large.The relative sliding between the soil and the soil cannot be expressed,and the free deformation ability of the pipeline is weakened to some extent.The research in this paper is based on the SPH-FEM coupling algorithm to study the dynamic response process of pipelines under soil landslide.Through research and analysis,the following conclusions are obtained:(1)The existing full-scale landslide experiment is simulated and reproduced,and the simulation results are compared with the experimental results.It is proved that the simulation method of the gas pipeline under the landslide is reasonable,compared with the traditional displacement load-driven pipeline.The finite element simulation,SPH-FEM coupling method results are more suitable for the actual situation,can better simulate the dynamic process of soil particle scouring and flow around the surface of the pipe,but it's calculation time is correspondingly longer;(2)Establish a practical working condition example,numerically simulate the gas pipeline under the soil landslide,analyze the change process of the soil around the pipeline and the maximum stress cross section of the pipeline during the landslide process,and find the pipeline to the soil.The body landslide has a certain resistance,and the maximum stress point of the pipeline gradually changes from the junction of the landslide to the landslide to the center of the landslide with the increase of the displacement of the landslide;(3)Simulated and analyzed the influence radius of different SPH particles,landslide displacement,landslide width,pipeline internal pressure,soil properties and buried depth of pipeline,and analyzed the influence of various factors on pipeline dynamic response.The results show that the displacement of the landslide has a fundamental impact on the stress on the pipeline.At the same landslide displacement,the landslide width has a significant effect on the maximum stress point of the pipe,which is because the landslide width is less likely to cause stress concentration on the pipe.Under different soil conditions,when the soil is sandy,the stress caused by the impact of the landslide is the smallest.When the soil is clay,the pipeline is subjected to the most stress.The stress and axial strain of the pipeline are positively correlated with the buried depth of the pipeline.As the buried depth of the pipeline increases,the pipeline stress and axial strain increase will also increase.The buried depth of the pipeline is 1.5m and the internal pressure of the pipeline is lOMPa.When the displacement of the landslide is 0.8m,the pipe stress has reached 606.1 MPa,which almost reaches the yield limit a of the X80 pipe.(4)Conducting on-site data survey and analysis on the pipeline of ZG natural gas pipeline in a landslide area in Guizhou,and establishing a numerical model based on the actual topographic data to simulate the stress of the pipe section of the landslide area,and obtain a multi-section stress concentration pipe section,which can focus on this pipeline.Stress monitoring,preliminary evaluation of pipeline safety,technical support for pipeline treatment engineering measures,initial pipeline reference for pipeline strain monitoring and early warning,and basis for the formulation of pipeline stress release scheme.