Failure Behavior of the Thermal Treated Granite under Triaxial Cyclic Loading-unloading Compression

Abstract

The failure behavior of thermal treated granite under triaxial tiered cyclic loading-unloading compression has a significant effect on the safe and stable operation of HLW disposal repository. Therefore, the stress-strain curves, elastic modulus, Poisson's ratio, plastic strain, dissipated energy and failure characteristic of the thermal treated granite specimens under triaxial compression were analyzed by experiment and numerical simulation. The results indicate that the elastic, Poisson's ratio, axial plastic strain, dissipated energy and accumulative AE counts slightly increase with cyclic loading at initial loading and elastic deformation stage when T = 25 and 300°C, which means that less damage was induced by cyclic loading. However, damage occurred once cyclic loading was applied when T = 600°C. Radial strain even showed compressive characteristic in the initial stage, which indicates that grains adjustment occurred under triaxial cyclic loading-unloading compression. And, the compressive characteristic is more obvious with the increase of temperature or the decrease of confining pressure. The failure modes under triaxial cyclic loading are more complicated than that under triaxial monotonic loading, which make the shear plane rougher. Therefore, the residual strength is higher than that under monotonic loading. When T = 600°C, micro-crack continuously increases under uniaxial unloading and loading process, which result in a decrease of the peak strength under cyclic loading compared with that under monotonic loading.