Investigations into Mining-Induced Stress–Fracture–Seepage Field Coupling in a Complex Hydrogeology Environment: A Case Study in the Bulianta Colliery

Abstract

The effect of mining-induced multi-physics coupling, characterized by stress–fracture–seepage field coupling (SFCC), is critical to safe mining and environmental protection. We investigated the spatiotemporal characteristics of the SFCC at the #31401 panel of the Bulianta Colliery. Changes in overburden movement, groundwater level, and groundwater inrush were monitored by means of borehole and working face observations, water leakage, and real-time video imaging. The results indicate that the distribution of mining-induced fractures was dominated by the key stratum, distributed as a “ladder shape” 30–75 m above the coal seam. The fracture penetrated into the lower key stratum and developed into the confined aquifer with a height of 140.5–154.0 m, while being truncated by the higher key stratum. Horizontal and vertical fractures developed sequentially in the confined aquifer-disturbed zone. Initiation, propagation, and interconnection of the seepage channel occurred in the fracture field, mediated by the redistributed stress. An abnormal discharge of 120–300 m3/h along the direction of mining commenced at the transition of the lower key stratum to the higher key stratum, and concentrated below the Bulian Gully. A fracture height model was developed based on the vertical fracture propagation, and mining parameters were modified, including reducing the mining height and increasing the advance rate and support resistance of the longwall mining face to effectively reduce the SFCC effect.