Features of Shear Strength Parameters Reflecting Damage to Rock Caused by Water Invasion-Loss Cycles

Aiming at the slope stability problem caused by the change in the water level in an open pit mine tailings pond, the weakening of the rock shear strength parameters (i.e. cohesion and internal friction angle) and the variation of Drucker-Prager strength yield criterion parameters have been analyzed. Based on the results of the tri-axial compression tests under different water invasion-loss cycles, they show the following: (1) The shear strength parameters decrease with increasing number of cycles. The cohesion of altered granite-1 has been reduced from 5.61 to 0.35MPa, and the internal friction angle has been reduced from 49.24 degrees to 22.70 degrees. As for altered granite-2, the cohesion has been reduced from 7.18 to 1.07MPa, and the internal friction angle has been reduced from 51.16 degrees to 25.64 degrees. (2) The degree of deterioration the shear strength parameters decreases with number of cycles. The cohesion decreases by 93.76%, and 85.09%, the internal friction angle decreases 53.89% and 49.88%. (3) According to the value of shear strength parameter subjected to water invasion-loss cycles, the variation law of different types of Drucker-Prager strength yield criterion has been determined. The exponential functions between the parameters and the number of cycles have been developed.