Energy-Driven Damage Constitutive Model of Water-Bearing Coal Under Triaxial Compression

A theoretical basis for evaluating safety and stability of underground engineering is to study changes in rock strength and failure. In the process of coal mining, the failure mechanical properties in coal present a complex change principle that, under various in situ stresses and in a hydrological environment, results in material failure because of its unstable state being driven by energy. Therefore, by establishing a relationship between energy change and deformation process of coal failure, it would contribute to reflecting the essential characteristics relating to coal strength and failure. In order to explore the mechanics and energy evolution characteristics of water-bearing coal under the triaxial compression process, triaxial compression mechanical experiments of coal under different water contents and confining pressures have been conducted in this paper, whose effects relating to different confining pressures, including water content on changes in total strain energy, elastic strain energy, and the dissipation energy of coal have been analysed. As coal is a porous medium containing a pore and fissure structure, the volume change law relating to coal during the deformation and failure process is characterised by porosity, consequently, a damage constitutive model for coal was established from the perspective of energy dissipation based on statistical damage theory. It is believed that this model could better reflect the deformation behaviour of coal under triaxial compression, in which the relationship between damage evolution characteristics and energy dissipation changes has been reflected in the model. Further, the methods of determining the model's parameters have been proposed to verify the rationality of the established model. Finally, the influence of confining pressure and water content on the brittleness in coal has been discussed from the position of energy evolution. Triaxial compression experiments were conducted on coal specimens to investigate the effects of water content and confining pressure on energy evolution.Based on statistical damage theory, the constitutive model that combined energy dissipation and coal failure was established.The effects of water content and confining pressure on the coal brittleness were discussed from the aspect of energy evolution.