Estimation of rock mass deformation modulus based on GSI system

Deformation modulus of a rock mass is one of the most important geomechanical parameters for a design and successful execution of rock engineering projects such as tunnels, dams, powerhouses. Field tests including plate loading, plate jacking, radial jacking, flat jack, etc, are the most commonly used methods to measure the deformation modulus of rock masses directly. However, these methods usually require extensive and difficult procedures and hence they are time consuming and costly. Thus, developing empirical equations to properly estimate the modulus of rock mass deformation on the basis of rock mass properties are of practical and economical advantageous. In this paper, at first, it is aimed at establishing an empirical predictive model for determination of the modulus of deformation based on GSI system using simple regression model. Then, the in situ plate loading test data and the rock mass properties are used to apply bivariate correlation analysis to determine the independent variables that affect on the modulus of deformation. Next, the results are used to develop a new empirical predictive model for determination of the rock mass deformation modulus with the aid of multiple regression analysis. This study includes a comprehensive credibility assessment of the prediction performances of some existing empirical equations as well. Subsequently, the results of the existing empirical equations were compared with that obtained by the equations proposed in this paper. Finally, it is concluded that the new empirical equation proposed in this paper provides more accurate results compared with the existing empirical equations.