Deformation analysis of transversely isotropic coal-rock mass with porous and cracks

Coal-rock as a typical sedimentary rock has obvious stratification, namely it has transversely isotropic feature. Meanwhile, deformation leads to coal-rock mass having the characteristics of different porous and crack structures as well as local anisotropy. Equivalent axial and circumferential strain' formulas of the pure coal-rock mass specimen with a single crack were derived through the establishment of equivalent mechanical model of standard cylindrical coal-rock specimen, and have been widely used to a variety of media combined different structures containing multiple cracks. The complete stress strain curve of a real coal-rock specimen was obtained by the CTC test. Additionally, according to the comparison with the theoretical value, the theoretical mechanical model could well explain the deformation characteristics of coal-rock mass and verify its validity. Further, following features were analyzed: strain normalized coefficient and elastic modulus (Poisson's ratio) in vertical and parallel direction to the stratification, stratification angle, porosity, pore radius, normal and tangential stiffness of crack, and the relationship of different crack width with different tangential stiffness of crack. Through the analysis above, it substantiate this claim that the theoretical model with better reliability reflects the transversely isotropic nature of the coal-rock and the local anisotropy caused by the porous and cracks. (C) 2012 Published by Elsevier B.V. on behalf of China University of Mining & Technology.