Strength of Models of Rock with Intermittent Joints

by Edwin T. Brown, (A.M.ASCE), Sr. Lect. in Engrg.; The James Cook Univ. of North Queensland, Townsville, Queensland, Australia,

Serial Information: Journal of the Soil Mechanics and Foundations Division, 1970, Vol. 96, Issue 6, Pg. 1935-1949

Document Type: Journal Paper


A series of triaxial compression tests were carried out on five sample types containing various patterns of preformed intermittent jointing. The 4-in. square by 8-in. high samples were built up from parallelepipedal and hexagonal blocks of high strength gypsum plaster exhibiting rock-like mechanical properties. Tests were carried out at confining pressures in the range 0 psi to 2000 psi. The seven modes of failure observed include axial cleavage and a dilational mode at low confining pressures, shear failure through the plaster, planar and non-planar shear failures partly through plaster and partly along the joints, and the formation of multiple conjugate shear planes at the higher confining pressures, either exclusively through the plaster or partly through plaster and partly along joints, the averaging process for calculating shear strength first proposed by the Austrian School of rock mechanics.

Subject Headings: Shear failures | Shear strength | Triaxial tests | Shear tests | Failure analysis | Structural failures | Structural strength | Strength of materials

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