Study On Fracture Development Law And Seepage Characteristics Of Surrounding Rock With Repeated Mining Under Insufficient Collapsed Gob

This dissertation focuses on the mining geological conditions of the coal seam group under insufficient collapsed gob of shallow coal seams,taking the Nanliang mine as the research background,comprehensively using the research methods of theoretical analysis,laboratory experiment,CT three-dimensional reconstruction inversion,numerical simulation and field measurement,taking the compaction characteristics of the insufficient collapsed gob,the fracture development law of the surrounding rock with repeated mining under insufficient collapsed gob,and the water and gas seepage characteristics as the research objects,The research results provide a theoretical basis for the prevention and control of water and gas in coal seam group mining.The main achievements are as follows:A confining compaction device which can realize CT scanning in-situ broken coal and rock is designed,and the acoustic emission characteristics,porosity characteristics and quality change characteristics of different particle sizes and different gradations of broken coal and rock are obtained.The sensor 3D semantic segmentation model is used to intelligently reconstruct the broken coal and rock mixture under different stress states,and the pore network model of the broken coal and rock mixture is constructed.The variation pore structure characteristics and pore and throat diameter are revealed.The random forest method is used to intelligently reconstruct the fractured rock,and the fracture network model of the fractured rock is constructed.The fracture characteristics of the fractured rock and the pore characteristics of the broken coal and rock mixture are compared.The compaction characteristics of the insufficient collapsed gob before and after repeated mining are studied,and the development law of surrounding rock fractures before and after the repeated mining under insufficient collapsed gob is revealed.The failure forms of surrounding rock before and after repeated mining are clarified.The fracture development degree of surrounding rock before and after repeated mining under insufficient collapsed gob is quantitatively characterized.The influence law of interlayer spacing on the fracture development characteristics of surrounding rock after repeated mining under insufficient collapsed gob is obtained.The water and gas seepage characteristics of broken coal and rock with different particle sizes and different gradations,elastic and fractured coal and rock and composite rock are studied experimentally.The coupling models of stress-pore-water seepage in saturated broken coal and rock and stress-pore-gas seepage in broken coal and rock are established.The evolution law of stress-gas permeability of fractured coal and rock is mastered,and the influencing factors of water and gas permeability of broken coal and rock are obtained.The influence law of interlayer rock fracture development degree on permeability is obtained.The fluid structure coupling discrete element model of repeated mining under insufficient collapsed gob is established.The seepage characteristics of surrounding rock after repeated mining under insufficient collapsed gob are simulated and studied.The influence of interlayer spacing on seepage characteristics of surrounding rock after repeated mining under insufficient collapsed gob is obtained.Applied to the practice of coal mine disaster prevention and control,this dissertation puts forward the relevant measures for water and air leakage prevention and control of repeated mining under insufficient collapsed gob,and realizes the safe and efficient mining of coal seam group repeated mining.The dissertation contains 124 figures,43 tables,and 182 references.