Influence of Initial Stress and Deformation States on the Shear Creep Behavior of Rock Discontinuities with Different Joint Roughness Coefficients

The sliding of rock blocks along rock discontinuities is caused by accumulated deformation and can result in disasters such as rock bursts and earthquakes. Creep along rock discontinuities leads to the accumulation of sliding deformation and random instability over time. The initial stress and deformation are important factors that strongly influence creep behavior. To investigate the influence of the initial state on the creep behavior of rock discontinuities, shear creep tests with loading–unloading shear pre-stress paths and shear creep tests with different initial stress and deformation states were conducted on artificial rock discontinuity samples prepared according to Barton’s standard roughness profiles. The creep behavior characteristics were investigated in detail according to the initial stress and deformation conditions. The results show that the initial stress and deformation states, which are related to crack development and plastic deformation accumulation, strongly influence creep behavior. Larger initial stress and deformation produce lower creep deformation, creep rates, and accelerated velocities. Samples with higher joint roughness coefficients produce more noticeable creep because more asperities provide additional space for creep to occur. A limit curve is also proven to exist, which allows the stress–deformation coordinate system to be divided into stable and unstable regions. When the current stress state of a sample is insufficient to drive the formation of further cracks or deformation in the rock discontinuity, the deformation and stress remain stable and no further creep is observed.