A comparative study for empirical equations in estimating deformation modulus of rock masses

The deformation modulus of rock masses (Em) is one of the significant parameters required to build numerical models for many rock engineering projects, such as open pit mining and tunnel excavations. In the past decades, a great number of empirical equations were proposed for the prediction of the rock mass deformation modulus. Existing empirical equations were in general proposed using statistical technique and the reliability of the prediction relies on the quantity and quality of the data used. In this paper, existing empirical equations using both the Rock Mass Rating (RMR) and the Geological Strength Index (GSI) are compared and their prediction performances are assessed using published high quality in situ data. Simplified empirical equations are proposed by adopting Gaussian function to fit the in situ data. The proposed equations take the RMR and the deformation modulus of intact rock (Ei) as input parameters. It has been demonstrated that the proposed equations fit well to the in situ data compared with the existing equations.

► The empirical equations for the estimation of deformation modulus of rock masses based on the RMR and GSI have been reviewed.
► Existing equations are divided into five groups and their reliability is assessed using the in situ data.
► Simplified empirical equations are proposed by adopting Gaussian function to fit the in situ data.
► The proposed equations fit quite well to the in situ data compared with the existing equations.