Empirical methods of calculating the mechanical parameters of the rock mass

The knowledge of the main mechanical constants of a rock mass (such as strength, deformability and the Poisson’s ratio) is one of the most important for rock engineering design on or in rock mass. Until now, several empirical relationships were determined for calculating these material constants based on both the quality of the studied rock mass (ie. RMR or GSI values) and the mechanical parameters of an intact rock. The goal of this paper is to review the empirical relationships between the mechanical properties of rock masses and the rock mass classification systems. The engineering properties involve not only the uniaxial compressive strength and deformation modulus of rock masses, but also Poisson’s ratio and tensile strength, among the others, which are of crucial for designing rock engineering structures. These different methods are compared and a general equation is determined in this paper.The presented expressions are yet to be tested with experimental data and empirical relationships should not replace in situ tests for final design.