Study on mechanism of delayed water inrush caused by mining-induced filling fault activation

Structural disasters and water inrush have always been the focus of coal mine safety. Existing research lacks consideration of the buffering effect of fault zones and the influence of internal structural characteristics on the evolution of the structure itself. To solve this problem, this article started with the internal factors of the structure, based on the rock mass limit equilibrium theory on the floor. The limit water pressure of the aquifer was deduced, the mechanical model of mining stress under the influence of faults was established, and the mechanical criterion of fault activation under the influence of mining was obtained. According to the mechanical criterion of fault activation, the internal fracture propagation of the fault under the action of confined water was obtained. The evolution characteristics of the water inrush channels was formed by the expansion and evolution of the internal fractures of the lower faults. At the same time, it is preliminarily proposed that the inhomogeneous force of the fault filling causes the unbalanced internal force of the fault, which leads to the lag in the connection of the water inrush channels and the delayed water inrush from the floor. The RFPA2D-FLOW two-dimensional numerical simulation software was used to simulate the process of floor fault activation and the final formation of hysteresis water inrush. Based on theoretical analysis and numerical simulation, the characteristics of floor fault activation and delayed water inrush induced by mining have been deeply studied, and the mechanisms of induced fault activation and delayed water inrush under the influence of mining has been obtained. The results show that when the working face passes through the fault, when the stress limit equilibrium state of the surrounding rock mass near the fault is broken, it is easy to promote the activation of the fault and induce water inrush disaster from the floor. At the same time, the unevenness of the fault filling and its buffering effect make water inrush is lagging behind. This water inrush mechanism provides a good reference for the prevention and control of water hazards in working faces where there is a risk of fault activation and floor lagging water inrush accidents, and it also has certain guiding significance for the retention of waterproof coal pillars.