Study On The Law Of Deformation And Failure Of Buried Pipelines During Longwall Coal Mining

In recent years,with the large amount of coal mining,the ground subsidence caused by coal mining had affected the safe operation of oil and gas pipelines,The instability of the pipeline had attracted the attention of the artisan and research scholar.But at present,the research on the safety of oil and gas pipeline was not mature,The study on the deformation and failure characteristics of pipeline caused by different mining stages in longwall mining was less.In this paper,the West-East Gas Pipeline in Shanxi haoyu coal mining area was used as the research object,using FLAC3 D to simulate large deformation,selecting the structural elements suitable for simulating the pipe-soil interaction,using MIDAS GTS NX to establish the three-dimensional model of undulating terrain,analysing the deformation and failure of pipeline in different mining stage,the simulated data and the actual monitoring data were compared to ensure the reliability of the model and the parameters of rock and soil.The research results in this paper provide the theoretical basis for monitoring and protection of buried pipelines in subsidence areas.The main conclusions are as follows:(1)The Liner structural element has the characteristics of thin shell and can simulate the interaction between pipe and soil,so it is more suitable for pipeline simulation in FLAC3 D.(2)The whole process of coal mining,the maximum subsidence point was located in the mining goaf center partial downhill,the surface near pipeline had uplift phenomenon in sixth step coal mining,the surface subsidence had sudden change in seventh step coal mining.(3)The pipe is deformed into a funnel shape,subsidence value increases gradually with the exploitation,the maximum subsidence point was located in the mining goaf center partial downhill in each mining stage.(4)In the sixth step coal mining,Pipe-soil separation layer began to threaten to the safety of pipeline,the pipeline has a large impending section.In the seventh step coal mining,the stress concentration phenomenon occurred in impending section onthe pipeline.(5)After the seventh step coal mining,the stress in the tensile stress zone of the pipeline is greater than the allowable stress,the maximum tensile stress is 4.42e8.The safety factor in goaf area(x=240m)was 0.92,which was in dangerous state;the safety factor of the stop mining line(x=410m)was 1.11,which was close to the dangerous state,and the compressive stress in all mining stages had not exceed the allowable stress on the pipeline;...