ABSTRACT
623This chapter reviews several key milestones in the study of pre-peak brittle fracture damage in rock, including both experimental and in situ observations and the conceptual advances that have arisen from these. What is recognized is that the strength of rock relative to brittle damage and failure mechanisms like spalling is considerably lower than the peak strength values measured through laboratory testing. Instead, pre-peak brittle fracture damage parameters such as crack initiation and crack damage serve as better indicators of the lower and upper in situ strength limits for brittle rocks. This understanding has led to the development of improved predictive tools for assessing the potential depth of brittle failure around deep underground excavations, as described in this chapter, together with the important role confinement plays in limiting and managing the brittle damage and failure process.
