Abstract: Since engineering rock mass is under high stress conditions, it has strong time-dependent effect due to continuously high ground stress after excavation and rupture. The study of creep properties after its post-peak is significant in both theory and practice. Firstly, the uniaxial pre-peak yield and post-peak rupture unloading tests are conducted on the intact rock samples using RMT-150B rock mechanics test system. Then the rock samples with different damage degrees are prepared under conditions of pre-peak yield and post-peak rupture. Lastly, uniaxial creep tests on the prepared rock samples are conducted to obtain uniaxial creep mechanical properties by using RLW-2000 microcomputer servo rock triaxial rheology testing system. From experimental results, velocities of all damaged rock samples show different degrees of reduction by comparing with the velocities of intact rock samples. Under each stress level, instantaneous dependent variable of the damaged rock samples gradually increases with the increase of the stress level, and there is linear relationship between the instantaneous dependent variable and stress level. It is found that the instantaneous dependent variable of post-peak damaged and rupture rock sample is significantly greater than that of pre-peak yield and damaged rock sample under the same stress level. Generally, each creep deformation gradually increases with the increase of the stress level under all stress levels, which meets exponential function relationship. The creep deformation of post-peak damaged and rupture rock sample is substantially greater than the pre-peak yield and damaged rock sample under the same stress level, Moreover, the difference of the creep deformation between post-peak damaged rock sample and pre-peak yield and damaged rock sample increases with increasing the load. The instantaneous deformation modulus of damaged rock sample steadily improved with the increase of stress level, furthermore, the instantaneous modulus changes linearly with the stress level. The instantaneous modulus of deformation at each stress level is obviously different, the higher the degree of rock damage, the lower the instantaneous modulus of deformation. For the damaged rock samples under all levels, the improved Nishihara model can be used to simulate uniaxial creep characteristics.

Key words: rupture rock sample, damaged rock sample, post-peak creep, uniaxial creep, creep model