A study on shear characteristics of a smooth rock surface under different thermal and mechanical conditions

Abstract

High-level radioactive waste repositories are designed to ensure longterm stability, and it is necessary to consider different effects at depth in various aspects. Many uncertainties are involved in characterizing rock mass eformation and failure in the designing process. The interactions between fluid flow, high temperature and stress disturbance must be considered. In this study, multi-stage triaxial compression tests were conducted to investigate the shear characteristics of a saw-cut surface of crystalline rock under different thermal-mechanical conditions. Granitic rock was taken from KURT (KAERI Underground Research Tunnel) for the tests. The artificial shear surface was cut, using diamond saw, at 28° from the direction of loading. The thermal-mechanical testing condition was decided by considering the actual condition at the vicinity of a canister. Three different confining pressures, 5, 10, 15 MPa, were applied during the test at two different temperatures 20° C and 80° C. The shearing behavior of a saw-cut surface was analyzed based on the Mohr-Coulomb failure criterion. From the experimental results, the shear characteristic of the granitic rock was observed to be sensitive to confining pressure but not to temperature. Numerical analysis was conducted using COMSOL to simulate the test, providing a good agreement with the experimental results. © Springer-Verlag Berlin Heidelberg 2013.