Experimental study on the dynamic mechanical properties and evolution mechanism of low-temperature frozen sandstone under impact loading

During the implementation of projects in cold regions or polar regions, the low-temperature freezing conditions significantly affect the dynamic mechanical properties of rocks, which influence the stability of underground engineering structures. In response, tests on the dynamic mechanical properties of rocks under low - temperature freezing were conducted. The effects of different low - temperatures (20 degrees C, 0 degrees C, - 20 degrees C, - 40 degrees C, - 60 degrees C) on the dynamic mechanical parameters (compressive strength, elastic modulus) of dry and water-saturated sandstones were analyzed. The variation of the damage coefficient under low - temperature freezing and impact loads was quantified. Models for inter-particle forces, water/ice-particle adhesion, and the relationship between macroscopic compressive strength and microscopic adhesion were established. The results show that: as the temperature continuously decreases from 20 degrees C to -60 degrees C, the dynamic compressive strength and elastic modulus first increase (from 20 degrees C to -10 degrees C) and then decrease (from -10 degrees C to -60 degrees C), the number of cracks in the specimens after impact first increases and then decreases. Under the same low-temperature condition, the compressive strength of water-saturated sandstone is higher than dry sandstone, while the elastic modulus of dry sandstone is higher than water-saturated sandstone. There is a significant positive corresponding relationship between the macroscopic compressive strength and the microscopic adhesive force of the sandstone. As the temperature decreases, they first increase and then decrease, and both reach the maximum values at -10 degrees C. The research results can provide theoretical references for ensuring the stability of engineering structures in cold regions.