Empirical Strength Criterion for Rock Masses

TLDR

An empirical strength criterion for rocks and rock masses is proposed. The criterion is nonlinear, incorporating intact rock uniaxial compressive strength and two dimensionless parameters, m and s, that vary with rock type, interblock friction, interlock, and anisotropy, and the authors provide approximate relationships linking these parameters to rock‑mass quality indices. These relationships have proven useful in preliminary design calculations for slopes and underground excavations in jointed rock.

Abstract

An empirical strength criterion for rocks and rock masses is proposed. The nonlinear criterion includes the uniaxial compressive strength of the intact rock material and introduces two dimensionless parameters, m and s. The parameter m varies with rock type, the angle of interblock or interparticle friction and the degree of block or particle interlock. The parameter s varies from 1.0 for intact rock material to zero for granular aggregates and depends on the interparticle tensile strength and the degree of interlock within the rock mass. For anisotropic rock, both m and s vary with the orientations of the planes of weakness to the principal stress directions. Approximate relationships between rock type, rock mass quality indices, and the rock mass strength parameters m and s, are presented. These relationships have been found useful in preliminary design calculations for slopes and underground excavations in jointed rock.