Coupled hydromechanical responses around a roadway excavation in inclined coal–mudstone strata

Abstract We conduct a numerical investigation into the spatio-temporal evolution of excavation-induced disturbances around roadways in inclined coal–mudstone strata containing fracture networks. The intact rock is modeled using a Mohr–Coulomb plastic constitutive law to capture deformation and failure, while the displacement of pre-existing fractures is governed by a nonlinear stress–displacement relationship in both normal and shear directions. Fluid migration through the fractured porous medium is described by Darcy’s law, and hydromechanical coupling is incorporated to account for stress redistribution, pore pressure variation, plasticity development, and fracture deformation during excavation. The simulations demonstrate that the in-situ stress ratio exerts a primary control over the magnitude and extent of excavation-induced responses, with higher stress ratios intensifying plastic yielding, shear stress concentration, and fracture slip. The dip angle of strata further influences failure patterns, as inclined formations facilitate failure localization along coal–mudstone interfaces, progressively shifting the disturbance behavior from mechanically-dominated to structurally-controlled regimes. In addition, excavation-induced stress redistribution produces rapid pore pressure transients in the low-permeability matrix, which in turn promote fracture shear activation and rock damage. These findings highlight the critical role of coupled hydromechanical processes in excavation-induced rock mass responses, with important implications for improving roadway stability and excavation design in various underground engineering applications.