Laboratory Study of Rock Joint Strength and Stiffness under Confining Pressure.
Technical rept. Feb 71-Feb 73,
UTAH UNIV SALT LAKE CITY DEPT OF MECHANICAL ENGINEERING
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A laboratory investigation of jointed rock is presented. Tests on jointed specimens of Nugget sandstone, Cedar City tonalite, and Pedernal Hills granite were carried out. The tests were conducted in a triaxial cell at confining pressures up to 40 ksi giving joint normal stresses in excess of 100 ksi. A small number of torsion tests on jointed specimens was performed. The peak joint strength was found to be approximately the same for the three rocks tested and is a nonlinear function of the normal stress. The results matched well with an overall curve presented by Byerlee, supporting the contention that friction is relatively independent of rock type. Residual friction on surfaces modified by deformation was found to be given by Mu 0.63. Joint stiffness in normal and tangential directions is presented, obtained by special gages placed directly over the joint. The tangential stiffness was found to be dependent on normal stress. A coupling of tangential and normal displacements during joint slip was observed. Author
- Geology, Geochemistry and Mineralogy