Continuum characterization of jointed rock masses: Part II—Significance of low shear modulus

Abstract

Finite element analysis is used to compare the displacement fields given by an anisotropic continuum model of a jointed rock mass with that obtained from the discrete joint model. The models have been described in Part I of the paper. These computations reveal excellent agreement between the finite element predictions of the joint model and the continuum model, except in the region of steep stress gradients near the loaded area. The anisotropic continuum model predicts a stress distribution that is significantly different from Flamant's solution for a strip load on a semi-infinite rock mass. Stresses are transmitted to a considerably greater depth along joints and to some extent across joints. This tendency is more pronounced in a medium of very low shear modulus, which corresponds to a joint set of low shear stiffness. Three case histories have been analyzed to evaluate the elastic behaviour of rock masses. These investigations suggest that actual rock masses may behave as a medium of low shear modulus. In this paper, attention is focused on the ddverse effects of low shear modulus on the stability of rock masses.