Long-term creep of Beishan granite under uniaxial compression

Investigations into the long-term creep behavior of Beishan granite in uniaxial compression were conducted. Four levels of axial stress (60, 70, 87, and 95 MPa) were applied to rock specimens. Contrasting with earlier research, the long-term creep data in this work present a substantial advancement in the time dimension. Except for the sample subjected to 60 MPa axial loading, which did not fail after a loading duration of 1650 d, the specimens under the other three stresses all failed after sustained constant loading durations of 1204, 1023, and 839 d, respectively. A lower envelope of driving stress-ratio for crystalline rocks was obtained, tending towards approximately 0.45 over an infinite time scale. According to the experimental results, as axial stress increases, both the axial strain accumulated in the transient creep process and the strain rate associated with steady-state creep deformation increase exponentially; however, the share of steady-state creep strain remains nearly constant at about 82.53 %. A novel damage-based creep model was put forward. It provides an enhanced depiction of the comprehensive creep process in rocks, notably improving the accuracy in forecasting the accelerated creep phase, which significantly impacts the long-term stability of engineering structures.