Research On Evolution Law Of Mining-Induced Water Resisting Property Of The Two Groups Of Clay Aquicludes In Thick Coal Seam Mining In Jinjitan Coal Mine

The mining technology of Yushen mining area in Northern Shaanxi is superior,but the ecological environment is fragile,so it is necessary to practice the concept of water conservation mining.The structural stability and evolution law of the aquiclude under the influence of thick coal mining are directly related to the protection effect of aquifer water resources.Based on the geological characteristics of aquifer,aquiclude and overburden in Jinjitan coal mine,in this paper,theoretical analysis,3D solid-liquid coupling physical simulation,FLAC3D-PFC3D numerical simulation and other methods were used to study the meso damage and failure law of the soil samples of two groups of clay aquicludes and the evolution law of the mining-induced water resisting property of the two groups of clay aquicludes with different mining methods under the thick coal seam mining.The main conclusions are as follows:(1)The law of progressive damage and permeability change of soil samples in Baode laterite and Lishi loess layers during triaxial loading and unloading was studied.The deformation,damage and failure of the structure,changes in porosity and permeability coefficient were analyzed from the meso-angles view of velocity field,displacement field,microcrack development,force chain field and bonding state of the particle system.It's found that the volume strain of soil samples,the compactness of the particle system,and the porosity are mainly controlled by the confining pressure during loading and unloading.The change of soil sample permeability is controlled by both the pore structure and the fracture structure.The relational equation of soil volumetric strain-permeability coefficient was obtained by fitting.(2)A 3D solid-liquid coupled physical model was built to study the water level change characteristics of the surface aquifer on the two groups of clay aquicludes,and the evolution law of the deformation,failure and water resisting property of the two groups of clay aquicludes in the process of layered mining of thick coal seams was revealed.The results show that:? In the process of upper layer mining,the overburden of the working face successively subsides and migrates from the bottom to the top,and the two groups of clay aquicludes produce cooperative deformation and damage,but the overall structural stability is not damaged,and the water level of the aquifer is kept at a level.?In the process of lower layer mining,the repeated mining disturbance aggravates the deformation of the two groups of clay aquicludes,the amount of plastic damage and deformation gradually accumulates,and the microcracks gradually produce,develop,and penetrate,which leads to the overall structure instability of the two groups of clay aquicludes,the rapid decline of the water level of the aquifer and the loss of water resisting performance.(3)The influence of different mining methods on the dynamic evolution of the mining-induced water resisting property in the two groups of clay aquicludes has been quantitatively studied.The damage degree of the two groups of clay aquicludes caused by different coal mining methods is gradually slowed down,in the order of high mining height and fully mechanized mining,full thickness of fully mechanized top coal caving and large mining height and layered comprehensive mining.The mining-induced water resisting property of the loess layer is destroyed first,and the damage degree is far greater than that of the laterite layer.Nevertheless,the mining-induced water resisting property of the laterite layer remains good.The overall the mining-induced water resisting property distribution of the the two groups of clay aquicludes is divided into the initial permeability increase zone,the permeability increase zone of the upper soil layer,the permeability recovery zone,and the permeability increase zone of the lower soil layer.The paper has 100 picture,16 table,and 118 reference.