Prediction of groundwater table recovery affected by approximate shallow buried coal mining in semiarid region

Abstract：In order to analyze the mechanisms of groundwater table recovery in non-leakage of semiarid mining areas with approximate shallow buried coal mining,physical simulation tests were carried out to observe the drawdown which was confirmed to be of ＂cone of depression＂ shape.A single well mathematical model of dive recovery was set up based on the law of mining drawdown characters and then solved to predict the recovery time based on modified Theis equation.The results of the mathematical model were checked and compared with the results of the recovery time of physical model and measured flow of springs.The law and influence on geological environment of groundwater recovery were then analyzed.The results show that the approximate shallow buried coal mining resulted in instantaneous decline of water level,and regarded the symmetrical cone of depression by virtual pumping at a constant rate and the water recovery as the consequence after virtual pumping.Because of the rock and soil collapse in goaf as well as calculation error from the value of well function approximation,the recovery times of both mathematical and physical models needed 225 d and 300 d respectively,when the groundwater recovery reached 95% of the drawdown after mining.The error of mathematical model was 9.1% as checked by the measured flow curves of springs near to the working face.Groundwater table recovery was quick in early stage but slowed in later stage and this led to reduction of crop yields in the large area during early stage,degeneration of vegetation reversibility and remission of land desertification.