Stability Criteria for a Composite Clay-Overlying Strata Aquiclude During Mining Under a Loose Pressurized Aquifer

Aquicludes may become unstable during mining under loose pressurized aquifers, resulting in water inrush and sand burst at the working face. To deal with this problem, we established a mechanical model for a composite clay-overlying strata aquiclude during mining under a loose pressurized aquifer. We used the principles of the minimum potential energy and force equilibrium to deduce a deflection function coefficient for each plate. Drawing an isoline between the stress component and the function showed that the plate can easily stretch and undergo shear failure at the midpoint of the long side along the advancing direction of the working face. We then used the Griffith yield and Mohr–Coulomb yield criteria to obtain an equation for the critical hydraulic pressure when the composite aquiclude fractures and becomes unstable. We used this equation to analyze example in the 312 working face of the qinan mine, the results showing that the maximum hydraulic pressure measured on site was 3.16 MPa, and it’s lower than the computed hydraulic pressure 3.87 MPa, so there is no risk of water inrush when advancing on the working face. Finally, the dynamic apparent resistivity test method was used to verify the correctness of the theoretical results derived in this paper.