Experimental Study on the Response of Cracked Sandstone to the Intermediate Principal Stress Coupled with Pore Pressure

Underground fractured rock masses are susceptible to failure under the combined influence of true triaxial stresses and pore pressure, posing severe threats to personnel and production safety of underground engineering. To investigate the influence of intermediate principal stress (σ2) on the mechanical and water diffusion volume change (ΔV) characteristics during the failure process of cracked rocks under stable pore pressure, this study conducted true triaxial strength experiments on cracked sandstone with stable pore pressure. The results demonstrated that with the increase of σ2, crack initiation stress (σci), crack damage stress (σcd) and the peak stress (σ1,peak) of cracked sandstone initially increase and then decrease. Conversely, ΔV tends to decrease first and then increase with the increase of σ2. This inverse relationship indicates that under elevated σ2, the decreased strength of cracked rock could lead to an increase in ΔV, which may increase the probability of water inrush disasters. The findings of this study provide a theoretical reference for the stability of rock mass engineering and the prevention of water inrush disasters.