Estimation of limestone rock mass deformation modulus using empirical equations

Determining the geomechanical parameters of rock masses at dam sites is a very important task. Different methods of determining these parameters have been proposed, depending on various factors such as the study phase, facilities, budget, and the time available. The deformation modulus is an important input parameter in any analysis of rock mass behavior. In the present study, the deformation modulus of the rock mass at the site of the Khersan II double-arch concrete dam was investigated using different field and experimental methods. The Khersan II Dam is located in the southwest of Lordegan, Chaharmahal Bakhtiary Province, Iran. The predominant formation at the site of the dam is the Upper Asmari limestone. The results of in situ tests such as plate load tests (PLTs) were analyzed to determine the deformation modulus, using the ASTM standard, Unal, and ISRM methods. These results were then compared to one another and interpreted. After that, engineering classification parameters such as RMR, GSI, and Q were evaluated at the same site that the PLTs were performed. Finally, the correlations between these classification ratings and the in situ deformation modulus of the rock mass were assessed, and some formulae for determining the deformation modulus of the rock mass at the Khersan II Dam site were derived. The accuracy and credibility of every formula was evaluated. These formulae for estimating the deformation modulus of the rock mass at the Khersan II Dam site were found to be highly accurate compared to other similar formulae.