Surface Settlement Of Goaf And Deformation Analysis Of Overlying Pipeline

With the development of China’s economy,pipeline transportation has become more and more prominent in various modes of transportation.Pipeline transportation has advantages that other transportation methods can’t match,but it also has great shortcomings,that is,it is greatly affected by natural geological conditions,especially when the pipeline passes through the coal mine goaf,the surface settlement of the goaf will be deformed.Safety has a big impact.In order to ensure the safety and stability of the pipeline when passing through the goaf,it is necessary to carry out calculation analysis and on-site monitoring of the surface settlement of the goaf,and at the same time,analyze the safety and stability of the pipeline according to the surface settlement deformation.(1)Selecting the rock movement calculation method based on probability integral method to calculate the ground settlement deformation on the working face of coal mine 54 mining area.The results show that the maximum settlement value of the ground surface after the mining is completed in the case of the near horizontal coal seam mining in sequence.It is 300mm,the maximum inclination value is 1.025mm/m,the maximum curvature value is 0.0053mm/m2,the maximum horizontal displacement value is 96mm,and the maximum horizontal deformation value is 0.498mm/m.(2)Using FLAC3D to simulate the mining of 54 working face in mining sequence,it can be found that the surface of the middle area above the goaf has the largest sinking value,the maximum sinking value is 240mm,and the maximum horizontal displacement is 90mm.And the maximum sink value and the maximum horizontal displacement value are not on one work surface.(3)After on-site monitoring of the entire mining area,it can be found that the actual surface maximum settlement of the 54 mining area is 260 mm and the maximum horizontal displacement value is 87 mm.Comparing the data of the 54 mining area on-site monitoring with the results of theoretical calculation and numerical simulation,it can be seen that Compared with the theoretical calculation,the numerical simulation results are closer to the measured values;while the 352 mining area uses the longwall slump method for coal seam mining,the measured maximum settlement is 1624 mm,which is the maximum surface settlement of the entire mining area.(4)By analyzing the existing pipe mechanics model of goaf subsidence area,including three-way soil spring nonlinear model,underlying soil pipe mechanics model and pipeline half-space force analysis model,the existing model is analyzed for pipeline.The shortcomings,based on the basic assumptions,establish a new mechanical model for pipelines in coal mine caving areas.(5)The analytical method given by the pipeline calculation model is used to analyze the mechanical calculation of the pipeline laid under uneven settlement conditions in the 54 mining area and the 352 mining area,and the ABAQUS finite element software is used to numerically simulate the pipeline,and the pipeline halfway in the mining subsidence area.The maximum axial stress of the force model is 45.1 MPa and 93.6 MPa respectively.The maximum axial stress calculated by the derived duct model of the mining area is 13.2 MPa and 49.8 MPa,respectively.The maximum axial stress obtained by the simulation is 18.99 MPa.67.93 MPa,the calculated model results are closer to the analog value.The failure criterion based on strain theory is adopted to evaluate the safety of pipelines.The conclusion that pipelines can be transported safely can be drawn by either the calculated value of the pipeline model derived by the half-space force model or the numerical simulation value.