Experimental research on the permeability evolution of different rock types under fluid-solid coupling conditions

The dynamic change of surrounding rock stress field in the roadway during the coal mining process leads to the development of fractures, resulting in the mining damage of overlying rock aquifer. As a result, the upper aquifer enters the mining space, increasing the risk of water inrush disasters in mines. Therefore, investigating the permeability evolution of fractured confined rocks under fluid-solid coupling conditions is of significant theoretical and practical importance. Focusing on the permeability evolution of the coal seam roof strata in the Shennan Mining Area under mining-induced disturbances, triaxial compression and permeability tests under fluid-solid coupling conditions were carried out on the typical weathered bedrock, sandstone, and burnt rock samples in burning area. Combining the acoustic emission monitoring results, the mechanical damage characteristics and permeability evolution patterns of different rock types were systematically analyzed, revealing the intrinsic mechanisms of permeability evolution under fluid-solid coupling effects. The results indicate that: The peak strength and secant elastic modulus of the three rock types exhibit a near linear growth trend with the increasing confining pressure, suggesting that confining pressure can enhance the rock strength while restricting the radial strain; There are differences between the acoustic emission ringing count and energy of different rock types, which is related to the mineral compositions. The confining pressure exerts a certain influence on the acoustic emission ringing count of different rock types; The permeability evolution of the three rock types under varying confining pressures can be roughly divided into four main stages, which correspond to the different stages of the deviatoric stress-strain curves; The variation trend of the acoustic emission damage variable is generally consistent with the permeability evolution. The node of permeability increase is near the crack initiation stress, indicating that the crack initiation and propagation of cracks are the dominant factors controlling the permeability evolution of different rock types. The experimental results can provide a theoretical basis for coal seam water conservation mining and mine water prevention in Shennan Mining Area.