Charts for estimating rock mass shear strength parameters

Charts are used extensively in slope practical application to meet the need of quick assessment of rock slope design. However, Charts for estimating the shear strength of the rock mass of a slope are considerably limited. In this paper, based on the Hoek-Brown (HB) criterion which is widely used in rock slope engineering, we present charts which can be used to estimate the Mohr-Coulomb (MC) parameters angle of friction <i>&#966;</i> and cohesion <i>c</i> for given slopes. In order to present the proposed charts, we firstly present the derivation of the theoretical relationships between the MC parameters and <i>&#963;</i>_ci/(<i>&#947;H</i>) which is termed the strength ratio (SR). It is found that the values of <i>c</i>/<i>&#963;</i>_ci and <i>&#966;</i> of a slope depend only on the magnitude of SR, regardless of the magnitude of the individual parameters <i>&#963;</i>_ci (uniaxial compressive strength), <i>&#947;</i> (unit weight) and <i>H</i> (slope height). Based on the relationships between the MC parameters and SR, charts are plotted to show the relations between the MC parameters and HB parameters. Using the proposed charts can make a rapid estimation of shear strength of rock masses directly from the HB parameters, slope geometry and rock mass properties for a given slope.