A continuum damage constitutive law for brittle rocks

The non-linear mechanical behaviour of two different granites was investigated. Short term triaxial tests have been performed in order to study the short term behaviour (instantaneous growth of cracks) of the rock. A continuous damage model is then proposed. The internal damage variable is directly related to the second order crack density tensor used by Kachanov in the study of effective elastic properties of cracked solids. An instantaneous crack growth criterion has been used to describe the time-independent evolution of the damage tensor. The verification of the model has been performed for various loading paths. The results of a numerical modelling show that it is possible to reproduce most of the observable characteristics of damaged zone around an underground opening excavated into brittle rocks. (C) 1998 Elsevier Science Ltd. All rights reserved.