Water Inrush Mechanism of Roof Induced by the Fault Weakening Effect in the Coal Mining

Abstract

The northern Guizhou coalfield exhibits complex geological conditions and well-developed structures. Hard rock formations are damaged by faults, causing frequent water inrush accidents. To study the damaging effect of faults on roof key strata and the mechanism of water inrush accidents, this paper chose the 5914 coal mining faces of the Longfeng coal mine as the engineering background, determined the water inrush source and key strata through field investigation, hydrochemical analysis, and theoretical calculation, and used RFPA-flow numerical simulation software to simulate the hydraulic coupling effect. The characteristics of the shear stress, damage degree, and hydraulic gradient were analyzed, and finally, the high-density electrical method was employed for simulation verification. The results indicated that the key stratum can control water inrush, but under the influence of faults, the roof forms multiple separation layers, and several sudden increases in displacement occur (the sudden jump phenomenon). A stress concentration area is formed in the head-end tunnel through the fault, and the number of AE events increased to 1150. The water-force gradient exhibits a uniform local large-scale evolution process, and finally, the height of the water-conducting fracture reaches 60 m through the aquifer. This height is 3 times that without fault influence. The numerical simulation results are consistent with the theoretical calculation and field analysis results, which verifies that the fault imposes a highly significant weakening effect on the key stratum, providing data support for later engineering.