Numerical Simulation Study On The Effect Of Coal Mining On Different Hydraulic Loose Aquifer Conditions In Thick Loess Covered Area

China is rich in coal resources,coal as the main energy,has an important role in the economic and social development,and the coal mining is also the destruction of groundwater environment.In Northwest China,coal mine often exists under thick loess layer,the loose aquifer in the thick loess layer is the main water source for local residents,due to the large number of mining coal mine in recent years,leading to the change of stratum structure above the coal seam,then the falling fractured zone appears,so that the overlying aquifer groundwater along the channel quickly lost,or increasing the recharge which from lower aquifer to underlying aquifer,direct impact on the residents' living water,indirectly undermine the groundwater balance in the region.Aiming at the problem that the coal mine is destroyed in the thick loess area,this paper is based on the research of Chang cun coal mine in Tunliu County of Changzhi in Shanxi,based on the investigation,collection and analysis of geological and hydrogeological data of the area,build the mathematics model of hydrogeological conceptual model,and the model was simulated using the GMS simulation of groundwater numerical model computer software based on the finite difference method.By changing the basis of loose aquifer hydraulic conditions,keep the distance between the falling fractured zone and the bottom of the aquitard is kept constant,and the thickness and the coefficient of aquitard are unchanged,to quantitative study the influence of coal mining on the loose aquifer with the loose aquifer hydraulic conditions.According to the simulation results,the main conclusions are as follows:(1)Before the coal mining in the study area,loose aquifer in dynamic equilibrium under natural conditions,when after the completion of coal mining,falling fractured zone formation,increase the loose aquifer groundwater recharge through down the flow of water flowing fractured zone,so that the groundwater level dropped significantly in the mining area,resulting in a drawdown cone,the influence range of the drawdown cone and the maximum drawdown decreased with the increase of time,and the change was larger in the early stage and the later was smaller.(2)Keep the distance between the falling fractured zone and the bottom of the aquitard is kept constant,and the thickness and the coefficient of aquitard are unchanged.To study the influence of coal mining on the loose aquifer with different permeability coefficient.Simulation results show,under different permeability coefficient,the influence area of the drawdown cone and the maximum drawdown are different,in the earlier stage of forecast,the permeability coefficient is large,then the influence area of the drawdown cone and the maximum drawdown are more large;in the later stage,the permeability coefficient is large,then the influence area is larger,but the maximum drawdown is smaller,the maximum influence area is 73.00km~2,and the maximum drawdown is 13.60 m.(3)Keep the distance between the falling fractured zone and the bottom of the aquitard is kept constant,and the thickness and the coefficient of aquitard are unchanged.To study the influence of coal mining on the loose aquifer with different hydraulic head.Simulation results show,under different hydraulic head,the influence area of the drawdown cone and the maximum drawdown are different,throughout the forecast period,the permeability coefficient is large,then the influence area and the maximum drawdown are larger,the maximum influence area is 74.90km~2,and the maximum drawdown is 18.81 m.