Experimental study on shear properties of red sandstone joints after cyclic wetting-drying treatment

In order to study the effect of wetting and drying cycles on the shear mechanical properties of jointed rock mass, joint samples with a JRC range of 5.20 ± 0.25 were selected by tilt test, and the direct shear tests of red sandstone joints with different numbers of wetting-drying cycles were carried out under constant normal stress. At the beginning of the wetting-drying cycle, the peak shear displacement of the joints increased first and then decreased, and increased after 8 wetting-drying cycles. As the number of wetting and drying cycle increased, the shear stiffness of joints gradually decreased, especially under low normal stress. After 16 wetting-drying cycles, the peak shear strength of sandstone joints decreased by 12.41%-23.77%. The influence of wetting and drying cycles weakened with the increase of cycle times, and the deterioration degree of peak shear strength of joints under high normal stress decreased. The cohesion and friction angle deteriorated significantly when the number of wetting and drying cycles is small. Under the same number of cycles, the degree of degradation of the cohesion is greater than the friction angle. The degree of joint surface damage increased with the increase of the number of wetting and drying cycles. After 4 wetting-drying cycles, the degree of damage tended to be stable. Under the action of wetting and drying cycles, the shear mechanical properties of joints are significantly degraded. The generation and expansion of cracks and fissures near the joint surface is the cause of the deterioration of shear mechanical parameters. © 2020, Science Press. All right reserved.