ABSTRACT
The two main ways in which rock can fail around tunnel, cavern and mine openings are by a) rock blocks falling or sliding into the excavation or b) the rock failing due to the concentrated stresses around the excavation periphery. The former case tends to occur at shallow depths where there is usually a greater jointing frequency; the latter case tends to occur at deeper depths where the in situ stresses are higher. Hoek et al. (1995) describe the process of rock failure and the associated support requirements in underground rock excavations.
