Rockbursts and secondary gas disasters are more likely to occur in complex geological structures, under the combined action of varied in-situ stress, mining stress and gas, which is the instability process of the mechanical balance system of coal media. Thus, it is the foundation of coal dynamic disaster incubation and occurrence mechanism, that describing the mechanical relationship of gas-bearing coal loading process accurately. In this paper, the primary crack is considered, defined as the initial damage and its theoretical derivation formula characterized by porosity is obtained, for the deterioration on the mechanical properties of coal. The damage evolution equation and mechanical constitutive model of gas-bearing coal based on non-uniform statistical theory is constructed, which the parameter of initial porosity, expansion of coal matrix gas adsorbed, softening characteristics of gas seepage and true triaxial stress state is considered, and the influence on mechanical properties is analyzed qualitatively. The result show that, the higher initial porosity of coal, the grater of length, width and number of cracks in any section, it's easier to form stress concentration with the effective area reduced, thus, the damage curve had a higher value at peak and a slight decrease in the growth rate of the post peak. Otherwise, the higher the degree of homogeneity, the lower the damage value at the peak, the more lagging the damage evolution is, and the greater the slope of the damage evolution curve. The expansion stress generated by coal adsorption improved significantly, with the increase of gas pressure, and the adsorption parameters a, b also promote it. The elastic modulus and homogeneity have a positive correlation on the strength of coal, and the modulus of stress reduction at post-peak, which increases the risk of coal burst liability. Both initial damage and gas promote the development of cracks in coal and reduced the uniformity of its properties, and then, the strength and stress drop modulus at post-peak decrease, while the plastic characteristics become more prominent and promote softening, it's also the reason why the rockburst happened in high gas coal seam with the risk indicators lower than conventionality. © 2021, Materials Review Magazine. All right reserved.
