Elastoplastic damage coupled model for gas-saturated coal under triaxial compression

An anisotropic damage, which is related to the plastic yield criterion, and a damage criterion are introduced to adequately describe the plastic deformation and the damage evolution of gas-saturated coal. The effective stress formulation for gas-saturated coal is derived by introducing the swell stress of gas adsorption into the effective stress principle of porous media. The damage law and the coupling effect between plastic deformation and material damage are represented sufficiently by using the framework of irreversible thermodynamics. On the basis of the experimental results, a general coupled elastoplastic damage constitutive model is developed for describing the mechanical responses of gas-saturated coal under various loading conditions by adopting a non-associated plastic flow rule. Moreover, the method for determining the constitutive model’s parameters is discussed. The comparison between simulation data and experimental data shows that the proposed model is able to depict effectively the main features of mechanical behaviors observed in gas-saturated coal.