Method for estimating the deformability of heavily jointed rock masses

Determination of the deformability of jointed rock masses is an important and challenging task in rock mechanics and rock engineering. In this paper, simple expressions are derived for estimating the equivalent isotropic deformation properties of heavily jointed rock masses using the methodology of equivalent continuum approach. The derived expressions are compared with two analytical relations in the literature and the field test data relating rock quality designation (RQD) and deformation modulus ratio E_m/E_r, where E_m and E_r are the deformation modulus of the rock mass and the intact rock, respectively. The derived expressions are in reasonable agreement with the existing analytical relations in the literature and satisfactorily predict the range of the field RQD versus modulus ratio E_m/E_r data. Finally two examples are presented to demonstrate the application of the derived expressions by applying them to estimate the deformation modulus of jointed rock mass at two sites. The results of the paper can be of help in predicting the deformation behavior of jointed rock masses when the properties of the intact rock and discontinuities are available.