During the excavation and using process of the High level nuclear waste (HLW) disposal repository, the surrounding rock bear the periodic loading, which has a significant effect on the safe and stable operation of HLW disposal repository. Therefore, GBM2D was adopted to investigate the mechanical behavior of thermal treated granite under triaxial tiered cyclic loading-unloading compression. The results show that the stress-strain curves of granite under cyclic loading are in good agreement with that under monotonic loading at room temperature, but cyclic loading lead to the grain fall off near the macro-crack. The difference of stress-strain between cyclic and monotonic loading is obvious when T = 600℃ under uniaxial compression, which due to that the increase of micro-crack during the loading and unloading process. However, confining pressure can restrain the increase of micro-crack during the unloading process and Felicity effect, and results in the difference of stress-strain curves between cyclic and monotonic loading decreases, but cyclic loading result in the grain crushing near the macro-crack. Due to a lot of thermal cracks were induced by high temperature when T = 600℃, elastic modulus increases obviously at initial loading stage, and it more sensitive to confining pressure.

Rock mechanics; Granite; Cyclic loading-unloading compression; GBM; High temperature