Creep behavior and permeability evolution of red sandstone in three Gorges Reservoir area subjected to cyclic seepage pressure

Abstract

The creep behavior of the rock mass in an anchoring section affects the control effect of the stabilizing piles and the long-term stability of the landslide-stabilizing pile system. Additionally, periodic reservoir water level fluctuations cause cyclic water-seepage pressure changes in the rock mass of bank slopes, which may promote rock creep deformation, further compromising the stability of the slope and increasing the risk of landslides. In this experimental study, the creep properties and permeability of red sandstone from the bedrock of the Majiagou landslide in the Three Gorges Reservoir area were investigated under cyclic seepage pressure conditions. Four seepage pressures (0, 1, 2, and 1-2 MPa) were selected for comparison. The results demonstrated that creep strain curves, especially volumetric strain, exhibited fluctuations under cyclic seepage pressure conditions. The creep deformation of red sandstone was enhanced by cyclic seepage pressure. Creep strain increased with increasing deviatoric stress, except at 60 MPa deviatoric stress. Furthermore, the creep time to failure at 108 MPa deviatoric stress was inversely proportional to the seepage pressure. The steady-state creep rate exponentially increased with deviatoric stress, and the steady-state creep rate under cyclic seepage pressure was higher than that under constant seepage pressures of 1 and 2 MPa. Finally, the permeability of the red sandstone fluctuated in accordance with the fluctuating seepage pressure. The permeability evolution of the red sandstone samples under different deviatoric stresses was attributed to the competing processes of preexisting microcrack closure and the propagation of new microcracks. Accurate evaluation of the long-term performance of stabilizing piles and the stability of stabilized landslides necessitates consideration of the influence of cyclic seepage pressure on rock mass creep behavior.