Empirical Strength Criterion for Rock Masses

by Evert Hoek, Principal; Golder Associates, Vancouver, Canada,
Edwin T. Brown, (M.ASCE), Prof. of Rock Mechanics; Dept. of Mineral Resources, Imperial Coll. of Sci. & Tech., London, England,

Serial Information: Journal of the Geotechnical Engineering Division, 1980, Vol. 106, Issue 9, Pg. 1013-1035

Document Type: Journal Paper


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.

Subject Headings: Rock masses | Rocks | Parameters (statistics) | Empirical equations | Strength of materials | Compressive strength | Granular materials | Ultimate strength

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