An alternative approach to estimate the shear strength parameters of intact rock

Engineering structures built on or within rock masses require a proper characterization of their geomechanical properties. In this context, determining the strength parameters of intact rock is essential. Triaxial compression (3XC) tests are routinely employed to determine the cohesion © and friction angle (ϕ) of intact rocks. However, this test not only involves inherent uncertainties but also typically requires a full day to complete a single set of samples. The objective of this study is to evaluate a more practical approach for determining the c and ϕ of intact rocks. For this purpose, 20 types of intact rock were tested via 3XC, uniaxial compression (UC), and single-shear (SS) methods. The internal friction angles were determined from UC tests, while the cohesion values were obtained from SS tests. The c-ϕ pairs derived from the 3XC tests were compared with those obtained from the UC and SS tests. The results indicate that SS tests tend to overestimate cohesion compared to 3XC tests, whereas UC tests generally underestimate friction angles. Overall, the findings suggest that the proposed approach has potential as an alternative testing method in rock mechanics.