A Strain Hardening and Softening Constitutive Model for Hard Brittle Rocks

To study the strain hardening and softening mechanism for hard brittle rocks, a strain hardening and softening constitutive model for hard brittle rocks is developed. First, the normalised hardening and softening factors are defined, which characterise the yield state of rock at the stages of pre-peak hardening and post-peak softening, respectively. Then, a unified strength parameter evolution model is established that can describe the nonlinear characteristics of cohesion and the internal friction angle under different confining pressures. Based on the Mohr–Coulomb criterion, a strain hardening and softening constitutive model is proposed. Finally, the proposed model was implemented in FLAC3D, and triaxial compression numerical tests of granite and diabase were conducted. The results show that the constitutive model can characterise the nonlinear mechanical behaviour of the pre-peak hardening stage and post-peak softening stage of hard brittle rock. The model was also able to satisfactorily capture the transition from brittle failure to plastic failure for hard brittle rock under high confining pressures.