Analysis of water-permeable fractured zone in weakly cemented overburden considering rock strain-softening

The accurate prediction of the water-permeable fractured zone (WFZ) height is critical for preventing water inrush disasters in longwall mining, especially in ecologically fragile areas. Current methods for evaluating the WFZ often neglect the strain-softening behavior of rock, leading to a commonly observed deviation in predictions. This study investigates the overburden failure mechanisms and WFZ development by integrating in-situ monitoring, empirical analysis, and numerical modeling using the Mohr-Coulomb (MC) model and an advanced Strain - Softening (SS) model. The SS model accurately replicated the progressive failure of the overburden, predicting a WFZ height of 144.5 m, which closely aligned with the in-situ data. In contrast, the MC model, with its assumption of constant post-peak strength, underestimated the height by 16 m, yielding a result of 128.5 m. This discrepancy concludes that the strain-softening behavior of rock is a dominant factor controlling WFZ development. Relying solely on traditional empirical formulas or simplistic constitutive models may lead to non-conservative underestimations of the WFZ, thereby escalating mining safety and ecological risks. The validated SS model provides a superior tool for realistic water hazard assessment and strategic mine planning.