The influence of mining stress paths on rock damage and permeability

To explore the stability control mechanism of surrounding rock during coal seam mining, the rock mechanical properties under the mining stress path were studied in this paper. The study begins by summarizing the mining roof and floor triaxial stress (MRTS and MFTS) paths through numerical simulations. The MRTS path is characterized by axial loading and confining unloading, while the MFTS path involves axial loading and confining loading. Subsequently, triaxial tests were conducted on rocks subjected to the mining stress path. The results indicated that compared to the standard triaxial stress (STS) path, the peak strength, peak axial strain, elastic modulus, and Poisson's ratio under the MRTS path were lower, whereas those under the MFTS path were higher. The MRTS path exhibited a more forward dilation deformation, rendering it more susceptible to damage, whereas the MFTS path displayed a more stable and backward dilation deformation. Tensile failure was primarily observed under the MRTS path, whereas the MFTS path resulted in shear failure. Furthermore, the study analyzed the variation of rock permeability with axial and volumetric strain. The relationship between permeability and axial strain follows a root shape, initially decreasing and subsequently increasing. The relationship between permeability and volumetric strain is found to be complex. Before the dilation onset point, the permeability decreases under both the STS and MFTS paths, while it decreases and increases slowly under the MRTS path. After the dilation onset point, the permeability increases under the STS and MRTS paths but initially decreases and then increases under the MFTS path. The research findings provide valuable theoretical guidance for mining strata control and water conservation mining practices.