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ORIGINAL ARTICLE

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

. Sheng-Qi Yang

Received: 1 May 2020 / Accepted: 25 June 2020 Ó Springer Nature Switzerland AG 2020

Abstract 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 (rcmax/rcmin) 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

P.-F. Yin  S.-Q. Yang (&) State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou 221116, China e-mail: [email protected]

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°. Keywords Transversely isotropic rock  Rock-like material  Strength  Deformation  Failure mode  Acoustic emission

1 Introduction It is often composed of two or more kinds of rock strata with different lithological characters and mechanical behavior in tunnel excavation section or extended direction, which can be regarded as composite strata. The layered composite rock mass can be approximated as transversely isotropy, and its behavior relevant to interface, the mechanical properties of each layer and orientation with respect to loading directions, hence, the mechanical behavior in this case can be different to that for an isotropic rock. For some sedimentary stratigraphy of coal mine, mudstone and sandstone distribute widely. Xiao and Qiu (1983) prepared a series layered composite rock specimens which composed of limestone, mudstone and sandstone. The layered composite rock specimen spliced by adhesives and the impact of interface

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Geomech. Geophys. Geo-energ. Geo-resour. (2020)6:44

cohesion was investigated (Xiao et