EXPERIMENTAL STUDY OF SHEAR FAILURE IN ANISOTROPIC ROCKS
Preliminary work has shown that planar anisotropy (foliation) may have a marked effect on both the breaking strength and the angle of shear fracture in rocks. For rocks experimentally deformed at room temperature and under low confining pressure, curves of breaking strength versus inclination of anisotropy are concave upward and parabolic in form. Shear fractures tend to develop parallel to well-developed planar anisotropy for inclinations up to 45°–60° to the direction of maximum pressure.