Abstract：Several groups of Brazilian split tests on heterogeneous gneiss considering the effects of different bedding orientations were conducted in order to investigate the influences of anisotropy and heterogeneity on failure behavior of rocks. The tensile strengths of gneiss with bedding structures of different orientations were obtained. The tensile strengths obtained can be considered as the one between the weak beddings of the minerals if the bedding orientation paralleling to the loading direction. If the bedding orientation is perpendicular to the loading direction，the obtained tensile strengths can be considered as the equivalent one of mineral grains of gneiss. But for other cases，the tensile strength is due to the combining effect of the tensile and shear failures，which deserves careful consideration in applications. A discrete numerical model was set up using UDEC. The bedding structures were modeled through assigning random distributed aggregates of deformable blocks and setting contacts between the bedding interfaces and the mineral grains. The numerical results have a good agreement with the experimental data，which explains the mechanism of fracturing failure modes. The study revealed that the failure of rocks was a self-organizing process of microcracks which was strongly affected by the microstructures of rocks.
TAVALLALI A，VERVOORT A，Effect of layer orientation on the failure of layered sandstone under Brazilian test conditions[J]. International Journal of Rock Mechanics and Mining Sciences，2010，47(2)：313-322.
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2014, Vol. 33 
