Background  Depressurization through dewatering using inclined wells arranged at the aquifer bottom represents a crucial technical approach to the prevention and control of water-sand inrush disasters during coal mining beneath aquifers. However, the mechanisms underlying seepage-pressure interactions and water-preserved depressurization remain poorly understood.

Methods  Based on the water-yield properties of confined aquifers and the distribution characteristics of inclined wells for dewatering, this study developed a fan-shaped sand tank experimental system for simulating dewatering and seepage from confined aquifers. Using the experimental system, this study carried out seepage experiments using a partially penetrating well at the bottom of a confined aquifer under varying well radii, well lengths, and dewatering pressures. Furthermore, the dynamic response characteristics of seepage and pressure were systematically analyzed.

Results and Conclusions  Under the influence of the elastic water release characteristics of the confined aquifer, pressure heads at various monitoring points exhibited short response and stabilization times after the dewatering pressure changed, with a pressure reduction zone formed near the inclined well at the aquifer bottom. In the case where the well length and radius were set at 40‒300 mm and 40‒100 mm, respectively, and the outlet of the drainage pipe remained full of water, negative pressure was formed within the well when the water level in the well was lower than the well head. The absolute value of the negative pressure rose as the well length and radius increased, with the negative pressure effect enlarging the pressure reduction zone at the aquifer bottom. Increasing the well length significantly enhanced the dewatering rate, provided that the well length was less than the critical value (250 mm). Increasing the well radius, despite also enhancing the dewatering rate, is difficult to implement in engineering practices. Besides, the negative pressure suction effect could also increase the dewatering rate. In the initial stage of dewatering, water released from the aquifer was dominated by stored static water. Then, the released water quickly transitioned into boundary dynamic recharge following a first-order exponential law. Based on the specific pressure distribution pattern formed using dewatering wells at the aquifer bottom, this study proposed a novel hydrogeological model that enables the effective prevention and control of water-sand inrush disasters while also mitigating the drop in the total water level of an aquifer. This model offers a novel, feasible approach to water-preserved coal mining that balances mining safety and ecosystem conservation.