Micromechanics-based prediction of creep failure of hard rock for long-term safety of high-level radioactive waste disposal system

A high-level radioactive waste disposal project is under way in Japan. Isolation of the radioactive waste in a rock formation at great depth is considered as one of the promising disposal methods, Before proceeding with the disposal project, however, assessment of the long-term stability of rock mass surrounding waste packages is necessary. This paper presents a micromechanics-based model for predicting the creep failure of hard rock under compression. The subcritical crack growth due to stress corrosion cracking and interaction effects between cracks are considered as the main mechanisms of creep failure. An evolution problem of two interacting cracks is formulated and creep failure following tertiary creep is represented as unstable extension of the interacting cracks in the present model. The time to failure is calculated for different values of axial stress, confining pressure, and environmental conditions such as temperature and presence of water. The effects of water, temperature. and stress states on the long-term behavior are also included in the proposed model. (C) 2002 Elsevier Science Ltd. All rights reserved.