A reliability model to predict failure behaviour of overlying strata in groundwater-rich coal mine

Abstract Coal mining in groundwater-rich coal fields will trigger failure of overlying strata, resulting in the formation of water-conducting fracture zone (WCFZ) and potentially leading to water-inrush accidents. In this study, a reliability model with consideration of spatial variability and uncertainty of strength parameters was proposed to predict the failure behaviour of overlying strata during coal mining in groundwater-rich coalfields. Rock strength parameters, including cohesion, internal friction angle, uniaxial tensile strength, and softening coefficient, are treated as random variables to determine the rock failure uncertainty. The experimental results of these geomechanical parameters at different positions are interpolated by the Kriging interpolation method. Spatially, the interpolated values are arranged as the average value of each random variable to demonstrate their autocorrelation. Furthermore, based on Mohr–Coulomb yield criterion, a performance function is deduced to calculate the failure probabilities of overburden rocks to evaluate the spatial scale of WCFZ. As a typical case, the failure features of adjacent overlying strata of No. 7121 mining face in Qidong Coal Mine is analyzed. The results show that the risks of water-inrush are high when the mining face advances to 260–380 m and 1120–1240 m, which aligns with both field monitoring results and borehole observation results. The proposed model holds significant implications for prevention of water-inrush accidents in groundwater-rich coal mines.