Study On The Law Of Surface Subsidence Underthe Action Of Mining Overburden And Water Environment

Based on on-site monitoring and theoretical analysis,this paper discusses and studies the law of surface subsidence under the action of the water environment.Based on the geological mining conditions of the Qisan mining area of Wuyang Mine,the effects of long-term mining on the overburden confined aquifer and surrounding water wells were studied.Through the comparative analysis of surface water and different depths of confined aquifers,the hydraulic connection between surface water and mine water is given.Based on the engineering background of Huainan Xieqiao Mine,Yongmei Chensilou Mine and Kailuan Linnancang Mine constructed an error function model of horizontal moving point in the subsidence basin boundary,and analyze the law of mining surface subsidence under thick water-bearing alluvium.The angular value parameters and probability integral prediction parameters of surface movement of each mine were obtained.Analysis of the difference of the rock migration law between the general geological mining conditions and the nature of the cause of subsidence abnormal parameters were interpreted.Based on the principle of effective stress,the mechanism of surface subsidence under the combined action of mining overburden and water environment was analyzed.Construct a calculation model of soil aquifer and confined aquifer in the coal seam under thick alluvium,and verified the model based on the measured data.The results show that:(1)Even if the diversion fissure zone is not developed to the bottom of the aquifer,the water level of the aquifer above the mine area may still be reduced to some extent due to the drainage of mine;due to mining,Wuyang Coal Mine In the Quaternary aquifer,the water level dropped by 7.36 m,and some wells appeared dry,with the maximum spread to the boundary of the gob area of 400m(the average working depth of the working face is 205m).(2)Under the condition of thick water-bearing loose layer,the measured horizontal movement range of the subsidence basin edge is larger than the subsidence range,and it is more reasonable to use the horizontal movement point of 15 mm as the boundary of the subsidence basin.(3)When mining under thick water-bearing alluvium,due to the proportion of bedrock is relatively small,the surface subsidence is mainly concentrated above the gob area,and the subsidence coefficient is too large(Xieqiao Mine 0.98,Chensilou Mine 0.9,Linnan Cang Mine 0.91)),the range of surface subsidence spreads widely,and the convergence is slow.The measured maximum sinking zone is 453 m.(4)Coal mining under thick waterbearing alluvium,the decline of phreatic level or pressure head is the root cause of sinking anomalies at the edge of subsidence basin.The calculation results of the compression model of the aquifer and the confined aquifer are compared with the on-site monitoring results of the Sondex sedimentation instrument.The predicted mean square error is ±8mm,and the relative mean error is 6.5%.The models can be used to predict and calculate soil consolidation induced by alluvium dewatering as underground coal extraction.