The deformation modulus of rock mass is an important parameter for the design of underground structures and foundations. In this study, 3 new equations with statistical analyses were developed for estimation of rock mass deformation modulus using a database of 47 plate loads, 86 dilatometers and 9 flat jack tests in Bakhtiary Dam Project in Iran. Finally, by data processing and the statistical analyses, the best new equation was suggested for the estimation of deformation modulus in Bakhtiary Dam.
Deformation modulus is one of the most important parameters in rock engineering projects. The deformation modulus of a rock mass is measured by in situ tests, such as dilatometer and plate load or flat jack tests. Also, in situ tests are expensive and time-consuming. Therefore, the deformation modulus of a rock mass is often estimated indirectly from classification systems. Many authors have developed several empirical models for estimation the deformation modulus by classification systems such as RMR, Q, GSI, RQD and RMI like Bieniawski, 1978; Serafim and Pereira, 1983; Nicholson&Bieniawski, 1990; Mehrotra, 1992; Grimstad & Barton, 1993; Mitri et al., 1994; Hoek & Brown, 1997; Read et al., 1999; Palmstrom & Singh, 2001; Barton, 2002; J. Carvalho, personal communication, 2004; Galera et al., 2005; Hoek & Diederichs, 2006. Also, Mohammadi & Rahmannejad, 2009 and Khabbazi et al., 2012, estimated rock mass deformation modulus by using regression and artificial neural networks analysis and a rock mass classification system, respectively.