DEM fluid–solid coupling method for progressive failure simulation of roadways in a fault structure area with water-rich roofs

Faults are common large geological structures in underground coal mining, and roadways near faults are seriously damaged. When faults connect aquifer roofs, the roadway surrounding rock (RSR) softens in the long-term water invasion process, resulting in more serious deformation. In this paper, taking the Beixinyao Coal Mine as the research object, the UDEC-Voronoi numerical model is used to study the progressive failure process of the RSR when a roadway passes through the fault under the condition of rich-water roofs. Based on the quantitative relationship of water immersion weakening of rock samples in laboratory tests, a fluid–solid coupling simulation method and a damage quantitative index suitable for the engineering scale are put forward. On this basis, the progressive failure characteristics of the RSR under the roof aquifer are simulated. The result shows that the fault activates the aquifer to form a seepage channel under the action of roof water pressure and mining stress. After water immersion, the mechanical strength of the coal and rock mass decreases, resulting in the development of cracks. Under the primary support conditions, the damage ratio in the study area is 63.3%. Among them, the number of shear crack events is 4.5 times the number of tensile crack events in the failure process of the RSR. According to the progressive failure characteristics of the RSR from water-rich roofs, a control strategy of dewatering the roof aquifer near the fault and strengthening the roadway support is proposed. The subsidence of the headgate roof is reduced by 65.9%.