A new empirical approach for prediction of rock mass strength based on a strength reducing curve zone instead of unique strength reducing curve

As is well known from rock mechanics literature, the mechanical parameters of a rock mass cannot be obtained by conventional laboratory tests due to the difficulties encountered in the preparation of cores from a rock mass containing discontinuities. To overcome these difficulties, researchers have focused on developing empirical equations for predicting stress-strain behavior of a rock mass, including based on measurements of the discontinuity patterns. However, the UCS value of rock mass (UCS _RM ) can be predicted by decreasing UCS _i based on quality of rock mass such as Rock Mass Rating (RMR), Geological Strength Index (GSI), Q value, etc. For this reason, an empirical equation in a unique reducing curve form has limited application in generalizing on the prediction of UCS _RM from particularly soft rock mass to hard rock mass. In this study, a new empirical approach is developed to be used for predicting of strength of rock masses from soft to hard rock masses. In addition, a new procedure for defining of the disturbance effect on the strength of rock mass is introduced to the new empirical approach in conjunction with Hoek and Brown failure criterion.