Use of the core strangle test for determining strength anisotropy of rocks

• Usefulness of CST in determination of strength anisotropy was evaluated.
• Performance of CST was compared with other indirect methods.
• CST was found as capable as and more precise than other indirect methods.
• Indirect methods are unadvisable in determination of strength anisotropy.
• Because anisotropy planes start to be parallel to loading axis after approximately θ=45°.

The usefulness of the core strangle test (CST) in determination of strength anisotropy and its accuracy compared with other indirect methods is evaluated. As a result of this study, higher accuracy was obtained, and CST led to considerably lower errors in determination of the strength anisotropy when compared with the results obtained from point load index and Brazilian tests. Moreover, it was found that CST may have a potential to be used as an alternative testing method for determination of strength anisotropy of rock core samples when a sufficient dimension cannot be obtained and/or when simple, fast and economical solutions may be needed. One of the most important results of this research is that the indirect methods should not be used in case the tensile stresses considerably contribute to total stresses in the failure of the rock material where the acute angle (θ) between the loading axis and the anisotropy plane is less than 45°.