Experimental study on dynamic tensile properties and energy evolution of sandstone after freeze-thaw cycles

In order to study the influence of freeze-thaw(FT) cycles on the dynamic tensile properties of sandstone, a φ50 mm split Hopkinson pressure bar(SHPB) was used to conduct dynamic Brazilian splitting tests on sandstone samples after different FT cycle numbers(0, 20, 40, 60, 80 and 100) under three loading rates(344.72, 371.991 and 431.761 GPa/s), and the change of the cores in the samples due to FT cycles were detected by a nuclear magnetic resonance system The damage characteristics, dynamic tensile strength and energy evolution of sandstone caused by FT cycles and loading rate are analyzed. The research results show that the FT sandstone degradation model satisfies an exponential function. As the number of FT cycles increases, the porosity and the degree of fracture increase, while the dynamic splitting tensile strength decreases. The degradation rate is the fastest after 80 FT cycles. The increase of the loading rate will weaken the degrading effect of the FT cycles on the sandstone and delay the half-life. The increase rate of the maximum absorbed energy caused by the rising of the loading rate decreases with increasing the damage degree. Meanwhile, the maximum absorbed energy decreases with the number of FT cycles in an exponential form while has a good positive correlation with the dynamic splitting tensile strength. The research results can provide a theoretical basis for the study of the failure mechanism of rock mass engineering in cold regions. © 2021, Science Press. All right reserved.