Effect of the Crystal Habit on Micromechanical Extensile Behaviors of Crystalline Rocks During Compression

The crystal habit controls the microstructure heterogeneity of the crystalline rocks that significantly affects their mechanical behaviors. However, thus far, this effect has not been quantitatively characterized. Here we establish a grain-based model to investigate the effect of crystal habit on compression-induced micromechanical extensile behaviors of the crystalline rocks. The grain morphology heterogeneity from euhedral to anhedral is qualitatively depicted by the fractal dimension ranging from 1.0844 to 1.0917. Meanwhile, the heterogeneity of the mechanical properties depended on the stress state is also taken into account. We identify two effects that affect the mechanical behaviors of the crystalline rocks: the tensile stress concentration effect (TSCE) and the grain boundary interlocking effect (ILE). These effects counteract with each other with varying crystal habit. As the crystal habit modulates from euhedral to anhedral, the stress threshold of the crack initiation of the crystalline rock generally decreases, while the stress threshold of the unstable crack growth and the peak stress first decrease and then increase. The transgranular failure zone mainly emerges adjacent to the unstable crack growth stage. With modulating the crystal habit from euhedral to anhedral, the number of the transgranular failure zone first decreases then increases; the produced intergranular cracks become scattered and shorter. Our results show that the crystal habit has important influences on the stress distribution characteristics and further affects the progressive failure characteristics of the crystalline rocks. We acquired new insights into the microcracking behaviors of the crystalline rocks that the anhedral microstructure favors the transgranular failure