Experimental Investigation on Dynamic Fracture Mechanism and Energy Evolution of Saturated Yellow Sandstone under Different Freeze-Thaw Temperatures

Abstract

The coupling effect of freeze-thaw (F-T) temperature and dynamic load on the dynamic mechanical properties and fracture mechanism of saturated yellow sandstone was experimentally investigated in this research. The dynamic compression tests on the specimen after different F-T temperatures (i.e., −5°С, −10°С, −15°С, −20°С, −30°С, and 20°С) have been carried out with split-Hopkinson pressure bar (SHPB) setup under eight F-T cycle numbers. The density and P-wave velocity of the specimens were obtained before and after the F-T tests. After the F-T tests, the specimen microstructures were examined via the scanning electron microscope (SEM). The dynamic fracture process was visualized by the high-speed camera. The particle size distribution and fragment shapes of the specimens were analyzed using a classifying screen. In addition, the energy dissipation law of specimens during the impact test was also discussed. Experimental results show that the dynamic elastic modulus, strength of the specimen, and the average particle size decrease with decreasing F-T temperature. SEM results reveal that low F-T temperature leads to severer internal damage of the specimen by inducing freeze-swell holes, interconnected cracks, and pore clusters. In addition, the fragmentation shapes of the failed specimens exhibit double-cone failure, single-side slope failure, double-side slope failure, and split failure. The energy dissipation increases gradually with increasing F-T temperature. This study helps to prevent geological disasters and optimize engineering design in cold regions.