Abstract:
To explore the rules of rock mass damage and permeability evolution induced by excavation of deep earth engineering, the triaxial tests under combined disturbance of cyclic loading and confining pressure unloading for simultaneous measurement of wave velocity and permeability are conducted. The damage and permeability evolution rules of red sandstone under different conditions are studied. The results show that: (1) The rock exhibits different stress-strain curve shapes at different stages of combined disturbance, and their end shapes depend on at which stage of disturbance the rock is failed. The initial stress ratio is the main factor to determine the difficulty of rock failure induced by the combined disturbance. (2) The total peak axial strain increases with the increase of the initial stress ratio, and the proportion of axial strain of the combined disturbance is always low. The absolute value of the total peak volume strain increases first and then decreases with the increase of the initial stress ratio, and the proportion of disturbance volume strain the combined is high. (3) At the initial loading stage, the wave velocity increases, and the permeability decreases. In the combined disturbance stage, the wave velocity decreases and the permeability increases. The damage and volume strain are approximately linearly related, and both the damage and permeability show a slow and then fast growth trend with the increase of disturbance times, and the inflection point seems to be on a straight line. (4) The rock exhibits a single shear failure mode at the combined disturbance unloading confining pressure stage, and a conjugate shear failure mode at the combined disturbance cyclic loading stage. (5) The double-high condition (high initial stress ratio and high initial confining pressure) will significantly increase the risk of excavation instability and failure of rock.