Rock anisotropy is well-known and is of considerable interest in the field of rock engineering mainly because of difficulties in rock mechanical characterization. A proper understanding of rock mechanical anisotropy is required for the design and construction of foundations, in tunneling and in slope stability investigations. Therefore, mechanical characterization of anisotropic rocks has been and is a subject of research with enormous importance. This study focused on characterization of indirect tensile and uniaxial compressive strengths of schistose rocks from the Singhbhum Shear Zone, India. Applicability of point load and block punch index tests in predicting uniaxial compressive strength of these rocks was also evaluated. For every available angle (β) between foliations and collected core axis (when β≠ 0°), equivalent specimens were tested under Brazilian test condition taking 6 different angles (β/s) between loading direction and traces of foliations on the core end face (when β/ = 0°, 15°, 30°, 45°, 60°, 90°) into account. The study suggests that while characterizing Brazilian tensile strength of schistose rocks, not only β/ is important, the influence of β should also be aptly taken into account. The uniaxial compression test results showed that a positive linear trend of uniaxial compressive strength vs. β is apparent for the available range of β. This was found valid only for the specimens with the most prominent foliations that failed completely along these weakness planes under uniaxial compression. It was experimentally demonstrated that the block punch test could be of similar importance as the point load test in estimating uniaxial compressive strength of schistose rocks. In case of these index tests, the stipulation of a valid specimen failure mode by ISRM does not seem to be accurate for anisotropic rocks like schist.
Mechanical characterization of rock materials is of significant importance in rock engineering.
