crack initiation of transversely isotropic rock under brazilian test, analytically and experimentally

Brazilian tests are used to determine tensile strengths of rocks. failure mechanisms, and the strengths determined, are influenced by the configuration of the load contacts. most research on how to interpret brazilian tests is only valid for isotropic rocks. this study addresses brazilian tests on transversely isotropic rocks, experimentally and analytically, to identify failure conditions for a range of load contact types and anisotropy angles (representing orientations of the transversely isotropic planes with respect to direction normal to the loading). stress fields determined analytically and coupled with a failure criterion to infer locations where failure and crack initiations occur. the analytical results are compared with experimental observations through digital image correlation (dic) for transversely isotropic hawkesbury sandstone. it is found that anisotropy angles affect the locations of the crack initiations, with agreement between the experimental results and analytical solutions being observed. failure and cracking at a disc centre enables reliable determination of the indirect tensile strength. the equation for strength, including a stress concentration factor for a range of transversely isotropic elastic properties, is presented for use by practitioners and laboratory technicians.