Mining Damage And Response Mechanism Of Coal Measure Overburden Hydrogeological Structure

Coal mining process,influenced by mining action,the upper goaf hydrogeological structure will change,big change may lead to mine water inrush crushing sand mine production safety accidents,such as for mine safety in production as well as a serious threat to the mine personnel life safety and social wealth,in order to reduce the occurrence of such threats,guarantee the mining area coal seam can be orderly mining in our country,in this paper,the coal measures strata of hydrogeological structure of mining damage and response mechanism has carried on the exploration,for coal mine safety mining of the region to provide a reasonable basis.Based on the analysis of borehole data in the study area,the three-dimensional hydrogeological structure model of the study area was established by using GMS modeling software.The aquifer and aquiclude in the study area were generalized from top to bottom as loose aquifer,loess/laterite aquiclude,sandstone fissure aquifer and bedrock relative aquiclude,and the distribution state and morphological characteristics of the hydrogeological structure in the study area were macroscopic presented.According to the actual engineering geological conditions and similarity principle of Jinjiang coal mine 31105 working face,the mining damage law of the aquifer and aquiclude is studied.With working face advancing,the mined-out area expands unceasingly,for the mining-induced damage of aquiclude structure,the cause of coal seam in caving generated for the first time direct roof sandy mudstone aquiclude,began to enter the caving zone development phase,the direct roof sandy mudstone widespread failure of aquiclude and fracture zone rapid development stage,the overburden rock cracks up constantly in the development,the final height of crack zone development breakthrough sandstone at the bottom of the confined aquifer sandy mudstone aquiclude,the layer of waterproof performance began to fail.But for the aquifer structure,the mining damage mainly concentrates on the rapid development stage of the fracture belt,the fracture in the aquifer develops,the permeability increases,and finally the fracture belt connects the confined aquifer,and the water inrush accident occurs along with it.PCAS treatment was used to analyze the fracture development rule in the process of similar model test.In the process of coal seam mining,the development process of fracture affected by mining can be divided into four stages: generation-rapid development-partial penetration-partial closure.In the upper coal seam similar model including the layout of aquifer and aquiclude stress sensor,which summarizes the aquifer and aquiclude stress affected by mining action of the dynamic change rule: when there was a pressurized state closer to the point of coal seam,influenced by the coal wall support,when the coal seam mining is located in the points below,appear unloading phenomenon,rock caving or downward bending deformation;Moreover,the change of stress in rock strata under the influence of mining is from near to far,and the influence degree is small,and the influence time lags behind.The finite difference software FLAC3 D was used to establish a fluid-solid coupling numerical model to simulate the dynamic change law of seepage field in mining with the presence of seepage and verify the mining damage law of aquifer and aquiclude structures in similar model tests.Through the analysis of stress nephogram and monitoring stress curve,and the dynamic change of the development of the plastic zone,similar model test contains basically verified,mining damage law of aquiclude structure and dynamic change law of stress and seepage velocity vector diagram and the layout of the pore water pressure of aquifer monitoring data,the analysis of aquifer seepage dynamic change rule in mining.With the advance of the working face,the pore water pressure in the aquifer decreases first and then increases and resumes.The seepage velocity of the seepage field increases with the advance of the working face,and its range varies with the development of the plastic zone in the aquifer and aquiclude.It starts from the top of the sandy mudstone aquiclude directly,and finally penetrates the confined aquifer.Finally,the seepage velocity in the whole plastic zone presents an amplification trend.To sum up,the mining-induced damage and response mechanism of the hydrogeological structure of coal measures overburden is formed by the joint action of the failure law of water-bearing layer and water-resisting layer and the law of mining-induced seepage field in the process of mining.Under the influence of mining,the water-resisting layer at the top of the coal seam in the overburden collapses and causes cracks,resulting in the failure of its water-resisting performance.The water-conducting cracks extend upward to contact the aquifer,resulting in large-scale disorder of the mining-induced seepage field.