Stress Analysis Of Steel-Plastic Transfer Joints For Gas Pipeline Network Considering Ground Subsidence

As one of the key components connecting steel gas gate valve and polyethylene(PE)pipe in urban pipeline network system,failure of connect part between steel pipe and PE pipe due to ground subsidence,resulting in leakage of urban gas and threatening people's lives and property safety.Therefore,in view of the failure of steel-plastic transfer joints for gas pipeline network in the ground subsidence,the stress variation law of steel-plastic transfer joints in the ground subsidence is obtained by combining theoretical analysis with ANSYS finite element analysis,which provides some basis for the future study of buried pipelines.The main work of this dissertation is as follows:(1)The calculation model of vertical earth pressure is established.Based on the unified strength theory and the linear slip surface model,the vertical earth pressure calculation model suitable for steel-plastic transition joints is deduced.The model is compared with the Marston theory and verified by ANSYS finite element simulation test.The results show that the model built in this dissertation is suitable for the calculation of vertical earth pressure of rigid and flexible buried pipelines,and a moderate reduction should be made when the vertical earth pressure is calculated by using Marston's theory.(2)The stress variation law of steel-plastic transfer joint underground subsidence is studied.Based on the data of steel-plastic transfer joints for gas pipeline network,the effects of four parameters,including settlement amount,length of subsidence zone,diameter of pipeline and buried depth,on the stress variation of steel-plastic transfer joints for gas pipeline network are studied by using independent variable method,and the stress variation law of buried pipeline is obtained.The results show that the amount of subsidence and the length of subsidence zone have great influence on the stress.(3)The steel-plastic transfer joint is analyzed by ANSYS finite element method.Taking steel-plastic transfer joint for gas pipeline network as an example,the stress of steel-plastic transfer joint for gas pipeline network under the four parameters of subsidence amount,length of subsidence zone,diameter of pipeline and depth of burial is analyzed by using ANSYS finite element software,and the corresponding stress nephogram is obtained,and the results of theoretical analysis are compared.The results show that the results of finite element simulation test are basically consistent with those of theoretical analysis,which verifies the feasibility of theoretical analysis.Based on the comprehensive analysis,the specific measures for protection of buried pipelines are put forward from the point of view of design,construction and safe operation.At the same time,the theoretical basis and technical support are provided for the damage of buried pipelines in the ground subsidence.