Strain energy evolution characteristics and mechanisms of hard rocks under true triaxial compression

Abstract

The energy evolution processes and mechanisms between three hard rocks are studied using a strain energy analysis method under true triaxial compression (TTC). Using Beishan granite as an example, the change in the energy storage limit Umaxe, strain energy ratio and strain energy conversion rate for different σ2 and σ3 values is investigated. The research results indicate that within the scope of this study, the energy evolution processes and characteristics are largely similar at pre-peak, and notably different at post-peak. The energy storage limit Umaxe of the Beishan granite indicates an approximately slow increase with an increasing σ2, whereas its mean value shows a favorably linear increase with an increasing σ3. The elastic strain energy ratio shows a reverse relationship with that of the dissipated strain energy during rock failure. For an increasing σ2, the conversion rates of the total elastic strain energy Ue and the total dissipated strain energy Ud of the Beishan granite demonstrate a poor relationship at both pre- and post-peak. For an increasing σ3, the mean values indicate a favorable linear change at both pre- and post-peak. The total strain energy and total elastic energy of the different hard rocks increase with increasing σ2 or σ3 values at pre-peak, whereas the total dissipated strain energy increases with an increasing σ3 and decreases with an increasing σ2 at pre-peak. When the external conditions are not considered, the difference in the elastic and plastic deformation capacities, which influence the energy difference in different rocks, is influenced by the mineral compositions and microstructures of the different rocks.