A damage constitutive model for coal under mining stress and adsorption-desorption

Abstract

Coal mining can pose safety risks as mining stress and adsorption-desorption damage the coal in front of the working face. To address this, a damage model under the coupled influence of mining stress and adsorption-desorption was proposed by incorporating statistical damage mechanics and the effective stress principle. The method for determining model parameters was provided, and the model was validated through triaxial compression tests on coal containing methane. The model parameters were qualitatively analyzed, and the impact of parameters on the deformation and damage evolution of coal was also examined. The residual strengths of coal determined by previous classical models and the proposed damage model under various confining pressures were compared. The results mainly show that coal containing methane has distinct stages during triaxial compression, including compaction, elastic deformation, yield, strain softening, and residual deformation. The proposed damage model accurately tracks deformation and damage in a coal containing methane at varying confining pressures. An increase in Weibull distribution parameters causes peak stress and damage accumulation to start at a higher strain. Furthermore, a higher correction coefficient of residual strength results in a faster stress drop rate but lower residual strength of coal after peak stress. The proposed damage model accurately predicts the residual strength of coal under various confining pressures.