Investigation of the Multi-Scale Deterioration Mechanisms of Anhydrite Rock Exposed to Freeze-Thaw Environment.

Abstract

The deterioration of anhydrite rock exposed to a freeze-thaw environment is a complex process. Therefore, this paper systematically investigated the physical and mechanical evolutions of freeze-thawed anhydrite rock through a series of multi-scale laboratory tests. Meanwhile, the correlation between pore structure and macroscopic mechanical parameters was discussed, and the deterioration mechanisms of anhydrite rock under freeze-thaw cycles were revealed. The results show that with the increase in freeze-thaw processes, the mechanical strength, elastic modulus, cohesion, proportions of micropores (r ≤ 0.1 μm), and PT-Ipore throat (0-0.1 μm) decrease exponentially. In comparison, the mass variation, proportions of mesopores (0.1 μm < r < 1 μm), macropores (r ≥ 1 μm), and PT-II pore throat (0.1-4 μm) increase exponentially. After 120 cycles, the mean porosity increases by 66.27%, and there is a significant honeycomb and pitted surface phenomenon. Meanwhile, as the freeze-thaw cycles increase, the frost resistance coefficient decreases, while the damage variable increases. The correlation analysis between pore structure and macroscopic mechanical parameters shows that macropores play the most significant role in the mechanical characteristic deterioration of freeze-thawed anhydrite rock. Finally, it is revealed that the water-rock expansion and water dissolution effects play a crucial role in the multi-scale damage of anhydrite rock under the freeze-thaw environment.