Fluctuations in groundwater inflow induced by periodic fracturing of overlying strata with mining

Coal mining disrupts aquifer structures above coal seams, breaks the natural groundwater balance, and leads to significant water inflow into mines or the surface, potentially causing subsidence and other geological disasters. However, precise quantitative studies on aquifer damage and the resulting changes in groundwater flow during mining remain limited, restricting effective groundwater management. This study focuses on the Shaanxi-Inner Mongolia border region in China, the largest identified coal-bearing area. By combining physical similarity material simulations, aquifer numerical simulations, and in-situ monitoring, we analyzed pressure changes in aquifers during the mining process. The results show that initial deformation of the roof aquifer occurs at approximately 40 m of mining progress, with periodic weighting intervals ranging from 12 m to 28 m. When fractures form in the roof aquifer, the pressure in the surrounding aquifer increases periodically before gradually stabilizing. At approximately 140 m of mining progress, the peak advance support pressure is observed, and the vertical displacement of the roof aquifer reaches a maximum amplitude of 82%. Microseismic monitoring data further confirm the peak advance support pressure and the maximum vertical displacement amplitude. The height of the water-conducting fracture zone in the roof aquifer is estimated to be approximately 120 m. Groundwater inflow during face advancement shows two fluctuation patterns: a long-period “stair-step” increase at a large scale, with a step period of approximately 800 m, and a short-period “oscillatory” variation at a local scale, with an oscillation period of 16–48 m. These findings provide important insights for groundwater resource protection and disaster prevention in coal mining areas.