Dynamic Characteristics of Water Inflow from a Coal Mine’s Roof Aquifer

The static and dynamic inflow of water from the roof aquifer changes as mining progresses. We used a second-order dynamic model to describe the water inflow process. The parameters of the water inflow model were solved using actual drainage from roof aquifers at nine working faces in the Yuanyanghu mining area of the Ningxia Autonomous Region, China, as well as the peak water inflow values, their locations, the equilibrium values of water inflow, and their initial occurrence locations. The parameters of the second-order dynamic model of water inflow were inversely calculated. The peak values of water inflow without drainage were also calculated. The results indicate that pre-drainage of roof water significantly weakens the intensity of water inflow during the mining process, reducing peak values by more than 72%. The characteristics of the water-conducting fractured zones determine the major drainage locations, while the water-rich and water-conductive nature of the direct discharge aquifer affects the water inflow equilibrium values and initial occurrence positions. The results show that the model parameters and characteristic values of water inflow are determined by the hydrogeological nature of the roof strata, water-conducting fractured zone(s), and mining speed.