Brazilian Tests on Transversely Isotropic Rocks: Laboratory Testing and Numerical Simulations

The dominant anisotropy (foliation and bedding) of geological materials, especially of foliated metamorphic rocks such as slates, gneisses, phyllites or schists, and sedimentary rocks with bedding planes, leads to complex fracture mechanical behavior. A series of Brazilian tests on Mosel slate were conducted considering different foliation-loading angles. Fracture patterns and strength of samples were analyzed. In addition, the deformation process and failure behavior of the foliated rock samples during the Brazilian tests were simulated using the discrete element method. The influence of anisotropic strength parameters of weak planes was studied numerically. A diagram of failure mode distribution marked with typical failure fracture patterns for Brazilian tests of transverse isotropic rocks was developed, which results in better understanding of failure modes of Brazilian tests on foliated rocks and allows a more reliable interpretation of strength parameters. It reveals, how the microparameters influence the bearing capacity and failure modes of Brazilian tests for anisotropic rocks.