Fereidoun Rezaie - Assistant Professor, Research Institute of Earth Sciences, Geological Survey of Iran, Science And Research Branch, Islamic Azad university, Arak, Iran
Seyed Alireza Nosrati - Department of engineering, Science and Research Branch, Islamic Azad University

Determining the rock mass deformability module is one of the fundamental and most important geomechanical parameters. This module is defined as stress to loading strain ratio. As the in-situ tests entail such flaws as being costly, time-consuming and accompanied with test errors, using empirical equations in addition to the mentioned tests have been recommended. Reducing the test time and economic feasibility are among the advantages of using the empirical equations. However, the said relationships suffer from the fault drawback considering such limitations as the test location, etc.; thus evaluation of the empirical equations is necessary before they can be used for the analysis of the data of a certain country. This paper aims at determining the rock mass deformability optimized module using the data resulting from dillatometric tests performed on some hydraulic structures of Iran through the proposed empirical equations employing the Root Mean Squared Error method and Mean Absolute Relative Prediction Error. The obtained results that each one of the equations is suitably efficient only in a certain range of the rock mass score.The minimum RMSE in Serafim And Pereira and Gokceoglu et al indicating that the above equations have less error and value resulting from the MRPE method belongs to the Gokceoglu et al., that the above equations have less error and deviation compared with other equations introduced in this Research.

Deformability module, Dilatometric test, empirical Equation, Root Mean Squared Error method, Mean Absolute Relative Prediction Error