A MICROSCOPIC STUDY OF CREEP AND FRACTURING OF BRITTLE ROCKS BASED ON DISCRETE ELEMENT METHOD

To analyze the creep process and creep mechanism of rock at a microscopic scale, a numerical model of time-dependent deformation and damage was established by incorporating the parallel-bonded stress corrosion model into the Particle Flow Code^3D (PFC^3D). The numerical model was validated against laboratory results. The numerical results replicated the typical three creep stages including the primary creep, secondary creep and tertiary creep. Meanwhile, the numerical simulation results indicate that the time-to-failure of creep decreases gradually with the increase of the stress level, while the initial axial strain, initial lateral strain, initial volume strain and creep strain rate gradually increase in this process. The crack propagation pattern in the uniaxial creep test is generally identical to that in the uniaxial compression test and the tension cracks are dominant. The crack growth rate increases with time and sharply increases in the tertiary creep stage. In the stress-stepping test, the axial strain, lateral strain, volumetric strain and the final propagation mode of the model are the same as that of the single-stage creep test. In addition, the comparisons between two-dimensional and three-dimensional creep simulation show that the three-dimensional modeling is more suitable than the two-dimensional modeling.