Micromechanics model of gas saturated coal weakened by elliptical microcracks

Based on the analysis of the deformation and growth of a representative elliptical microcrack with arbitrary orientation and geometrical size embedded in a representative volume element subjected to triaxial stress and pore pressure, the additional compliance tensor induced by an embedded opening/closed elliptical microcrack is derived. Assuming numerous elliptical microcracks, and introducing an appropriate probability density function to describe the distribution of orientation and geometrical size of microcracks, the additional compliance tensor induced by microcracks system is analyzed in Taylor’s scheme, and a three-dimensional micromechanics model for gas saturated coal materials is obtained. The validity of the proposed micromechanics model is verified by the agreement between the theoretical and experimental results of gas saturated coal under triaxial compression. The effect of pore pressure and confining pressure on the damage behavior induced by microcracks is investigated. The calculations show microcracks of coal under higher pore pressure will be more inclined to slide and grow, and induce larger additional strain in the last deformation stage.