In this paper, the applicability of available correlations that estimate the deformation modulus from Rock Mass Rating (RMR) and Pressuremeter Test (PMT) to the Korean rock mass is evaluated. The correlations between deformation modulus and other rock properties were also analyzed. It appears that the existing correlations using RMR overestimate the deformation moduli and wide variation was found between predicted moduli and the measured values. Rock Quality Designation (RQD) and unconfined compressive strength (UCS) were found to correlate to deformation modulus reasonably well, but joint spacing and joint conditions appear to correlate poorly to RQD and UCS. Groundwater could not be correlated to the modulus. The measurement depth was found to have very little contribution to deformation modulus. However, it is estimated that poor correlation result from the fact that measurement depth is coupled with not only with the deformation modulus, but with other factors including strength, joint condition, and degree of weathering. The inappropriateness of the correlations clearly demonstrate that more in depth analysis techniques such as multivariate correlations is needed to better estimate deformation modulus of rock mass from available rock properties.
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