Numerical Simulations of How Staged Dewatering and Mining Influence Surface Subsidence

This paper reports a case study of a coal mine in Qidong in China’s Anhui province. Working face 613 was selected to study the aquifer compaction generated by each pumping stage and the surface subsidence pattern caused by each mining stage. A conceptual model of groundwater flow was established based on the hydrogeological data, and the pumping of the target aquifer was simulated based on the production plan of working face 613 in 2016. The simulation indicates that the water level in the central area dropped to − 306.45 m only 5 h after pumping; within 24 h, the water level dropped to − 500 m. In contrast, the aquifer compression had a lag, and only 0.015 m of compression was produced about 24 h after pumping. The aquifer compression at the pumping center reached a maximum value of 0.077 and the influence range was very small. The rock of the target working face was sampled and mechanically tested, and a FLAC3D numerical model was constructed following the borehole histogram and test results. Monitoring points were arranged at critical positions on the surface and stratigraphic contact surface. The subsidence variation pattern showed that each mining stage could be divided into three different periods of transmission, subsidence, and stability. Furthermore, the proportion of surface subsidence caused by pumping to the total subsidence value varies in each stage; the target aquifer produced a compaction value of 0.077 m, which is about 35% of the total subsidence at the end of the last stage. These results pave the way for more efficient mine water management in underground mines.