Theoretical and numerical studies on hydro-mechanical wing crack propagation in precracked rock materials considering T-stress

To examine the propagation mechanisms of wing cracks in rock under hydro-mechanical interactions, we developed a theoretical model that incorporates compressive loading effects, T-stress, and hydraulic pressure. Complementing this, a coupled hydro-mechanical-damage numerical model was employed for observation and comparative analysis. The influences of water pressure and confining pressure on wing crack evolution were systematically investigated. When T-stress effects are considered, the initiation angle of the compression-shear crack varies with the crack’s inclination, which is consistent with previous experimental results, as opposed to the initiation angle of 70.5° from the traditional theory. In the presence of water pressure, hydraulic forces transmitted within the cracks partially counteract the com-pressive stresses on the crack faces, thereby enhancing tensile damage. This results in an increased mode I stress intensity factor at the wing crack tip in the theoretical model, promoting both crack initiation and propagation. Conversely, an increase in confining pressure elevates compressive stress while reducing shear stress along the crack planes, which delays tensile damage and decreases the mode I stress intensity factor, thus inhibiting wing crack development. The numerical model effectively visualizes both the crack propagation process and the associated flow field, with simulation outcomes demonstrating good agreement with theoretical and experimental results. These findings contribute to a deeper understanding of crack propagation and failure behavior in geotechnical engineering contexts.