Construction and application of overburden damage and aquifer water loss model in medium-deep buried coal seam mining in Yushen mining area

Overburden deformation and damage caused by coal seam mining is the main cause of water loss from aqui- fer. This paper aims at the problem of limited research on the water loss law of aquifer under the influence of mining the medium and deep coal seams in Yushen mining area. According to the geological and hydrogeological structure characteristics of overburden rock of main mining seam in Yushen mining area,the authors summarize and put forward the “lateral direct and vertical leakage” combined water loss model of aquifer under the influence of damage and de- formation of overburden in medium and deep seam mining. On the platform of COMSOL multi-physical field coupled numerical analysis software,the method of constructing numerical analysis model of deformation damage of overburden and water loss of aquifer in medium-deep coal seam mining is put forward. ① Using the rock mechanics module of the software,the coupling relationship of overburden mining stress,porosity and permeability is established under the con- dition of coal seam mining. The displacement and deformation of each subdivision node of overburden in bending zone are simulated and the change of mining permeability coefficient is calculated. The Mohr-Coulomb plastic failure criteri- on is used to identify the range of water-conducting fracture zone under mining disturbance. ② The secondary subdivi- sion mesh under mining deformation is formed by relying on the auto-subdivision function of large deformation geome- try in COMSOL software platform. ③ According to the transformation characteristics of groundwater flow between aqui- fer and water-conducting fractured zone,the range of mining-induced aquifer fractured zone is numerically treated as Darcy seepage boundary,and re-input the parameters of mining permeability coefficient in the Darcy seepage analysis module. Finally,taking Caojiatan Coal Mine in Yushen mining area as an example,an analysis model of deformation damage of overburden and water loss of aquifer in coal seam mining at working face scale is established. the simulation results show that the maximum height of water-conducting fractured zone is 128 m under the condition of stratified mining (5 m mining height) the 2-2 coal,which develops into the aquifer of bedrock of Zhiluo and Yan’an Formation results in 35. 84 m3 / h of total water loss,and the lateral direct loss and the vertical loss are 23. 17 and 12. 67 m3 / h respectively,which has little influence on the loose aquifer. The maximum height of water-conducting fractured zone is 202 m under the condition of full mining height (10 m mining height),and develops into the weathered strata with well water abundanc3e,results in 130. 31 m3 / h of total water loss,the lateral direct and vertical water loss increase to 92. 65 and 37. 66 m / h respectively,which has great influence on loose aquifer.