Simulation and analysis of the effect of water preserved mining in open-pit coal mines in burned rock areas

Open-pit mining can cause strong disturbance to the adjacent burned rock aquifer. This paper takes an open pit mine in northern Shaanxi Province as the study area, and through numerical simulation, the changes of groundwater flow field and mine discharge in the study area without reserving water-preserving coal pillars and under the conditions of reserving 20 m, 50 m and 100 m coal pillars are simulated, and the effect of water-preserving mining is evaluated. Further, the water resistance performance of the grouting curtain when the burst water occurs during mining was analyzed. The results show that: the disturbance of coal mining to groundwater decreases with the increase of the width of water- preserving coal pillar, reserved 100 m coal pillar can reduce the burn rock water yield by more than 86%, the maximum depth reduction by about 13 m, and the impact area by about 60%; grouting curtain can effectively seal the centralized burst water point; the water yield reduced by about 90%, the observation hole water level restored about 4 m, the flow field restored gradually after sealed burst water point.