A model for estimation of stress-dependent deformation modulus of rock mass

Deformation modulus of rock mass has a significant role in the support design of an underground excavation. It is determined by expensive in-situ tests or by empirical models. Existing models for estimation of deformation modulus do not consider its stress dependence. Herein, data from several sources is used to develop a stress- (depth-) dependent relation for estimation of deformation modulus. The derived exponential expression incorporates the GSI, Youngs modulus and depth as input parameters for deformation modulus estimate. It is explained that at certain depth, the shear strength of rock joints will become close to the shear strength of a monolithic rock, and below this depth, the rock mass behavior is close to that of a monolithic rock, as well as the deformation modulus.