Microstructural approach in damage modeling

A microstructural approach is proposed for the modeling of brittle rock dam age. The basic idea of this approach is to model, not directly the mechanic al response of the rock but the changes in crack geometry. The term 'crack geometry' is used in the sense of Oda et al. (cf. Oda, M., Yamabe, T., Kame mura, 1986. A crack tensor and its relation to wave velocity anisotropy in jointed rock masses. Int. J. Rock. Mech. Min. Sci. 23 (6), 387-397). It the refore implies both a crack density and a spatial crack organization. As Ka natani, K. (1984. Stereological determination of structural anisotropy. Int . J. of Eng. Sci. 22, 531-546.) has shown, if the PL stereological paramete r is known, the accumulated crack length may be calculated in any direction , which in turn makes it possible to calculate the crack induced deformatio n for any given stress. Hence, our approach consists in formulating some la boratory-based laws for the evolution of Pr as a function of applied stress as well as the criterion for crack initiation and for macroscopic failure. Some of the laboratory tests used to elaborate and validate this approach are described in detail in the accompanying paper. The parameters of the pr oposed model are calculated for a granite and the results of the running si mulations are in good agreement with laboratory tests. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.