Stability Analysis Of Natural Gas Pipeline In Coal Mine Subsidence Area

The mining of coal seams in the oil-gas-coal overlap area caused the gradual migration and deformation of the overlying rock surface of the panel which caused the buried natural gas pipeline in the affected area of the subsidence zone to move and deform,causing the pipeline to break and fail,which seriously affected the oil-gas gathering and transportation.The safety and stability of the project,the normal production of panel.The Daniudi gas field in the Ordos Basin is a typical area for cross-exploitation of coal and associated resources.According to the geological situation of laying natural gas pipelines in the aeolian sandstone layer on the panel of Mou Coal Mine in the overlapping area,through theoretical analysis,numerical simulation and similarity Simulation and other test methods are used to clarify the mechanical characteristics and deformation evolution mode of buried natural gas pipelines under mining subsidence,put forward a safe distance control prediction method between natural gas buried pipelines and coal mining faces in aeolian sand subsidence areas.Achieve the following research results:(1)Using theoretical analysis and numerical simulation to study the stress and deformation characteristics of buried pipelines under the influence of mining,establish mathematical models for the deformation of buried pipelines at different mining levels,and conclude that the stress state of the top of the pipeline under vertical stress is changed from tension,the bottom is changed from pressure to tension;the top and bottom of the pipeline are both subjected to tensile stress under the action of horizontal stress,the direction of the force on the left and right sides of the inflection point is opposite.The research results show that the deformation of the buried pipeline in the mining subsidence area can be represented by the Gaussian function;the stress state of the top and bottom of the pipeline under the action of vertical stress is up and down,the center of the subsidence is left and right;the overall force state is about the center of the subsidence.symmetry.(2)Combining the main causes of deformation and failure of buried natural gas pipelines,design a monitoring test device for natural gas pipeline stress and deformation under load.A uniform load was applied to the middle of the φ48mm natural gas pipeline to monitor its stress and deformation characteristics.The results showed that the strain at the top and bottom of the pipeline increased with the increase of the load.The top and bottom of the pipeline were both compressed and the bottom was tensioned.The state is just the opposite;under the same load,the strain from the end to the center of the pipe shows a gradual increase trend,the strain increase at the top of the pipe is significantly greater than that at the bottom;the tensile force carried by the end of the pipe increases with the increase of the applied load.The two are in a positive quadratic function relationship;as the uniform load increases,the overall deformation of the pipeline evolves in the order of flat bottom,funnel,and triangular shapes,plastic failure has occurred when the pipeline deforms into a triangular shape.(3)Taking the aeolian sand subsidence area of Mou Coal Mine in the gas-coal overlap area as the engineering background,the subsidence is established by combining the Gaussian function of the surface subsidence curve,the movement track of the buried pipeline,the limit deformation and the surface subsidence curve.The prediction method of safety distance control of oil-gas pipelines in the area believes that the pipeline movement trajectory in the subsidence area points to the center of the mined-out area along the surface subsidence curve,its deformation is funnel-shaped;the prediction method takes into account the safety of oil-gas pipelines and mining,shortening the coal mining the distance between the panel and the oil-gas pipelines is reserved;it provides a new method for the pipeline layout in the gas-coal overlap area,rationally adjusts the coordinated mining under the oil-gas-coal resource co-extraction mechanism,provides new ideas for the coordinated development of coal-measure co-associated resources ideas.(4)Combining methods such as field observation and numerical simulation to carry out hazardous zoning of pipelines.According to the relationship between pipeline stability and surface deformation,0 ～360m along the advancing direction of the working face are divided into safe areas,360～620m are divided into dangerous areas,620～2000m are divided into safe areas;according to the limit deformation of the pipeline,subsurface the area with a settlement value greater than 128 mm is classified as a pipeline damage area,the pipeline with a surface subsidence value of 0-128 mm is classified as a dangerous area,the area with a surface subsidence value of 0 is classified as a pipeline safety area.