Experimental study on strength and failure behavior of transversely isotropic rock-like material under uniaxial compression

This study prepared transversely isotropic rock-like specimens in three groups of layer thickness ratios, alternating with two kinds of rock-like materials. The conventional triaxial compression tests confirm mechanical difference of the two rock-like materials. The velocities of ultrasonic wave (longitudinal wave VP) are measured for each transversely isotropic rock-like specimen before uniaxial compressive test, the results present an anisotropic behavior with the degree of longitudinal wave velocity anisotropy (VPmax/VPmin) of the three groups of transversely isotropic rock-like specimens are 1.44, 1.08 and 1.09, respectively. The uniaxial compression test indicates that the strength variation of the three groups of transversely isotropic rock-like specimens are “U-shaped”, with the degree of strength anisotropy (σcmax/σcmin) are 2.35, 4.42 and 2.08, respectively. An empirical failure criterion introduced by Jaeger and modified by Donath predicts the failure strength of transversely isotropic rock-like specimen well. The acoustic emission result shows that the AE ringing count is significant to the surface crack extending. The failure pattern of transversely isotropic rock-like specimens can be classified into one of the following three modes: (a) tensile-split along the core axes when small bedding angle (0°, 15°, 30°), (b) shear-sliding along the bedding plane when major bedding angle (45°, 60°, 75°) and (c) split along the vertical bedding plane when bedding angle of 90°.