Time-scale effect of the creep model parameters and particle flow simulation of sandstone with a single crack

The creep deformation behaviors of the hard rocks in deep high-stress environment, especially for the fractured hard rocks, cannot be neglected. To investigate the long-term creep deformation behaviors and the creep model for the fractured hard rock, the rocks with a single crack (α=45°) are obtained using the high speed water jet technology. The peak deviatoric stress (σ_p) of the fractured rock under a confinement of 30 MPa is obtained before single-step creep test. The applied creep deviatoric stress is approximately 80% of σ_p and the creep time is 539 h. The experimental results show that the fractured rock exhibits the primary and secondary creep deformations without the tertiary creep deformation and creep failure. To characterize the creep deformation behaviors of the fractured sandstone, a damage creep model based on the Burgers model and the effective stress principle is established. The parameters of the damage creep model determined by the least squares method show distinct time-scale effect. Therefore, a damage creep model considering time-scale effect is proposed to describe the creep deformation behaviors of the fractured hard rock under different time-scales. In contrast, the proposed model agrees well with the test data. Finally, the triaxial compressive tests and creep experiments are simulated using the particle flow code (PFC^2D). The numerical results agree well with the experimental ones. The research work may provide references for further investigations on the creep deformation behaviors and models for the fractured hard rock.