Mechanical Response Analisys Of Pipeline Subjected To Landslide Based On DEM-FEM Coulpling

As the lifeline of the national economy,oil and gas pipeline is the most economical,environmentally friendly and safest way to transport oil and gas.At present,the total length of pipeline in China has reached more than 100,000 kilometers,including four oil and gas strategic channels which are located in the Northwest,Northeast,Southwest and offshore area respectively,three vertical and four horizontal pipe corridors and the national backbone pipe network as well.Long buried underground pipelines sapn across a wide geographical area.Because the geographical environment is complex and changeable,the pipelines in service will inevitably meet with a variety of geological disasters,threats and damages.In recent years,with the increase in the number of extreme weather and geological disasters,landslides have become the main cause of pipeline failure accidents.Therefore,it is very important to study the mechanical response of the long-distance pipeline under the action of landslide to ensure the safe and reliable operation of the pipeline.Based on the research results of safety of buried pipelines under the action of landslide at home and abroad,this paper uses the discrete element method(DEM)and finite element method(FEM)to establish the analytic model of pipeline mechanical response under the action of landslide.The main contents and achievements are as follows:(1)EDEM,the discrete element software conducts the modeling and simulation of the movement of landslide soil,which is the discrete medium;ANSYS,the discrete element software conducts the modeling and simulation of the pipe,which is the finite element medium.In this paper,DEM and FEM are used to establish the one-way coupling simulation model of pipeline-landslide.The contact load of the particles in the discrete element simulation is derived and converted into the load of the corresponding node in the finite element analysis.After the calculation,the finite element analysis of the pipeline is carried out.(2)Based on the research data of landslide accident at Northeast Gas Field of Sichuan,the causes of pipeline landslide are analyzed,and the finite element model of pipeline-landslide foundation is established.(3)The repose angle of samples of landslide soil taken from Northeast Gas Field of Sichuan are measured and recorded,and the measured value of repose angle is regarded as calibration parameter,the four other contact parameters are the prepared-calibration parameter,and the orthogonal experiment that consists of 4 factors and 3 levels is built and executed by DEM software EDEM,the result value of one test group whose reposed angle is the closest to the measured value from 9 calibration tests is accepted;(4)The mechanical response of the pipeline under the action of landslide is analyzed by using the discrete element software EDEM,and the load at the maximum time point of the pipeline is imported into ANSYS for finite element analysis,and the simulation model is verified.(5)The effects of different particle models and sizes on the stress of the pipeline under the action of landslide are studied.The sensitivity of particle-particle contact parameters and particle-pipe contact parameters on the influence of pipeline stress under landslide is analyzed.The effects of pipe parameters such as pipe materials and specifications on the force of the pipeline under landslide are analyzed.The influence of design parameters such as depth on pipeline is studied and the corresponding measures to reduce the applied force of the lateral landslide are given.