Risk Assessment and Water Inrush Mechanism Study of Through-Type Fault Zone Based on Grey Correlation Degree

In order to effectively prevent and control the problem of water inrush from the through-type fault floor, based on the analysis of the case data of water inrush from the fault structure in the Fengfeng mining area, the types of karst water inrush from the floor are divided into 3 categories, 6 subcategories, and 17 fine categories. Four water inrush modes are summarized: composite structure water inrush, through-type fault water inrush, roof crack expansion water inrush, and floor vertical crack expansion water inrush. Based on the grey correlation theory and combined with the Analytic Hierarchy Process (AHP), this paper evaluates the water inrush risk of the F55-1 through-type fault zone from a micro individual perspective, taking the Xin'an Mine as the engineering background. Based on the water-rock coupling theory, the FLAC(3D) numerical simulation software is applied to study the disaster mechanism of the water inrush mode of the through-type fault. Through analyzing the changes of primary fracture stress and displacement of the intact floor strata and the aquifuge, and the pressure changes of confined water in fault zones, the collaborative water inrush mechanism of the damage and fracture of the bottom plate rock layer, the expansion and connection of the original fracture, and the seepage and progressive intrusion of the pressure water during the advancing process of the working face is analyzed. The research results indicate that the evaluation result of the water inrush risk of the F55-1 through-type fault in Xin'an Mine is Level I, belonging to the high risk and consistent with the actual situation model, verifying the rationality of the evaluation model. The process of water inrush in the numerical model is summarized as follows: a rock pressure failure zone is caused by the rupture and instability of floor aquifuge; a progressive intrusion zone develops-water inrush is connected between rock pressure failure zone and progressive intrusion zone; floor lagging flood occurs. Under the combined action of mine pressure and confined water pressure, the progressive intrusion height of confined water is significantly increased. The research results have important reference basis for future coal mining planning. This provides engineering reference and practical experience for the prevention and control of water damage in structured bottom plates under similar conditions.