An analysis of laboratory and long-term rock strength using a sliding crack model

The strength of rock is influenced by microcracks, and the growth of these cracks leads ultimately to failure. The theoretical model in this paper builds upon existing principles that relate rock strength to unstable crack growth in which the opposing crack surfaces slide across one another in shear. A relationship between mobilized frictional resistance and increasing shear displacement is introduced to describe non-linear strain behaviour observed in laboratory tests. The model also allows for unstable crack growth at stresses less than the peak laboratory strength.