Mechanical and microstructural properties of schist exposed to freeze-thaw cycles, dry-wet cycles, and alternating actions
Jiajia Gao, Jiajian Jin, Daguo Wang, Shaogang Lei, Jianguo Lu, Huan Xiao, Jinhe Li, Huadong Li
Abstract
In cold regions, slope rocks are inevitably impacted by freeze-thaw, dry-wet cycles and their alternating actions, leading to strength weakening and pore degradation. In this study, the mechanical and microstructural properties of schist subjected to four conditions were investigated: freeze-thaw cycles in air (FTA), freeze-thaw cycles in water (FTW), dry-wet cycles (DW), and dry-wet-freeze-thaw cycles (DWFT). Uniaxial compressive strength (UCS), water absorption, ultrasonication, low-field nuclear magnetic resonance, and scanning electron microscopy analyses were conducted. The integrity attenuation characteristics of the longitudinal wave velocity, UCS, and elastic modulus were analyzed. The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist. The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media ( R 2 >0.97). Different media affected the schist deterioration and half-life, with the FTW-immersed samples having a half-life of 28 cycles. Furthermore, the longitudinal wave velocity decreased as the number of cycles increased, with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles. Moreover, the damage variables of compressive strength and elastic modulus increased with the number of cycles. After 40 cycles, the schist exposed to FTW exhibited the highest damage variables and saturated water content.