Abstract: To investigate the effect of unloading rate on the unloading-induced slip behavior of cement grouting-reinforced jointed granite, a constant axial pressure graded unloading perimeter pressure induced slip test was carried out on the grouting reinforced jointed granite in the state of close to critical stress by using the TATW-2000 rock triaxial test system, The unloading rates are 0.1, 0.5, 1, 5, and 10 MPa/min respectively. The study showed that: (1) During the shear slip process, the rock-slurry bond interface undergoes abrasion, leaving numerous micro-scratches on the cement section surface of the granite. As the unloading rate increases, the JRC values are 17.52, 16.25, 15.65, 12.82, and 10.72, which indicates that the larger the unloading rate is, the smaller the micro-scratches on the surface of the cement section are. (2) The relationship between the average shear slip rate and the unloading rate during each perimeter pressure unloading period conforms to a power function relationship, and the average shear slip rate increases with the unloading rate, but the rate of increase gradually decreases. Under the influence of stress-strain hysteresis effect, the average shear slip rate in each perimeter pressure holding period also increases with the unloading rate. At unloading rates of 0.5, 1, 5, and 10 MPa/min, the average shear slip rates during the perimeter pressure holding period are much smaller than those during the perimeter pressure unloading period, and the relative difference between the average shear slip rates during the perimeter pressure unloading period and that during the perimeter pressure holding period is smaller at an unloading rate of 0.1 MPa/min. (3) The average shear slip rate of dynamic slip is one order of magnitude higher than the average shear slip rate of creep slip. The average shear slip rates for creep slip and dynamic slip increase with increasing unloading rate, while the duration decreases with increasing unloading rate. (4) When the unloading rate is less than 1 MPa/min, the peripheral pressure corresponding to the slip instability of the specimen is positively correlated with the unloading rate, and negatively correlated when the unloading rate is greater than 1 MPa/min.

Key words: rock mechanics, unloading-induced slip, unloading rate, jointed rock, shear slip rate