Sensitivity analysis of GSI based mechanical parameters of the rock mass

Abstract

The purpose of this paper is to analyze the sensitivity of the various constants of the different mechanical equations that depend on the Geological Strength Index (GS I) and the disturbance factor (D). Recently, both the Hoek-Brown failure criteria and the Hoek-Diederichs equations for determining the rock mass moduli are widely used in rock mechanics. For calculation these parameters, it is necessary to determine both the Geological Strength Index (GS I) and the disturbance factor (D). The results show that these parameters are very sensitive to both the GS I and the D factor, hence determining both them exactly is very important for the rock engineering design. Our results present the relationship between the uncertainties of GS I and D values and the uncertainties of the rock mass moduli. In order to establish good empirical formulas one should have some idea about the effect of variations in the input parameters for judging the acceptability of the design.