Estimating the Rock Mass Properties of Ultramafic Rocks in Central Greece Using the Triaxial Tests of Intact Rock and the Geological Strength Index

Due to the fact that the estimation of the rock mass properties is very important in any geotechnical project, many studies have become with the aim of their determination. But, the immediate determination is very difficult because the in situ tests are time-consuming, expensive and sometimes unreliable. For this reason, many researches have attempted to calculate the rock mass characteristic through empirical equations, but only few have focused on the ultramafic rocks. The main purpose of this study is to estimate the engineering properties of the ultramafic rock masses through the uniaxial compressive strength of the intact rock, the influence of blast damage, the material constant and the Geological Strength Index with the use of Hoek and Brown criterion (Roclab Software). Thus, sixteen samples, taken from central Greece (the western part of Othrys mt and the Kallidromo mt), were tested (uniaxial compressive strength and triaxial tests) and the results were statistically described and analysed. The manuscript reveals strong positive linear correlation between the estimated (through the Hoek and Brown failure criterion) uniaxial compressive strength and the measured (determined by strength tests) uniaxial compressive strength. The values of the uniaxial rock mass compressive strength, the global rock mass compressive strength, the rock mass tensile strength, and the rock mass modulus of deformation are finally calculated and presented. Furthermore, an attempt to correlate the rock mass deformation modulus (E_rm) with the tangent young modulus (E_i) results that there is high correlation between them both for peridotites and serpentinites.