Strain rate is not only an important influence factor for deformation property but also an important parameter for analyzing the dynamic mechanical behavior of rock material. In this study, the dynamic compressive mechanical properties of saturated yellow sandstone at four strain rates and six freeze-thaw temperatures are investigated by using the SHPB test system. The coupling effect of strain rate and freeze-thaw temperatures on the mechanical parameters of rock material are discussed in detail, and the relationship formula of peak strain and dissipated energy with strain rate and freeze-thaw temperature are also established. Finally, the fractal dimension characteristic of fracture specimens with the strain rate and temperature are analyzed by using the fractal dimension method. The research results indicate that (1) with the increase of strain rate, the increase speed of peak strain, peak strength, and dissipated energy at medium strain rate level was obviously higher than that at high strain rate level, indicating that the strain rate effect weakened at high strain rate. (2) Freeze-thaw temperature can improve the brittleness-ductile transformation rate of saturated specimens. (3) According to the strain rate sensitivity coefficient, at room temperature, the strain rate effects on peak strain and peak strength are weakest, while at -20°C ~ -30°C, they are most significant. In addition, the strain rate effect on dissipated energy is significant at room temperature, while weakest at -30°C. (4) The fractal dimension gradually increases with strain rate increasing or freeze-thaw temperature decreasing, indicating that the freeze-thaw environment has a positive function for increasing the damage and fracture degree of specimens for saturated specimen. Our research results can provide an extremely important theoretical basis for the dynamic disaster prevention and structural design of rock engineering in cold regions.

中文翻译：

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应变速率和冻融温度对饱和黄砂岩动态力学性能和分形特征的耦合影响

应变率不仅是影响变形特性的重要因素，也是分析岩石材料动态力学行为的重要参数。本研究利用SHPB试验系统研究了饱和黄砂岩在四种应变速率和六种冻融温度下的动态压缩力学性能。详细讨论了应变速率和冻融温度对岩石材料力学参数的耦合作用，建立了峰值应变和耗散能与应变速率和冻融温度的关系式。最后，利用分形维数法分析了断裂试样随应变速率和温度变化的分形维数特征。研究结果表明：（1）随着应变率的增加，中应变率水平的峰值应变、峰值强度和耗散能的增加速度明显高于高应变率水平，表明应变率效应在高应变率下减弱。(2)冻融温度可以提高饱和试样的脆韧转变速率。(3)根据应变速率敏感系数，室温下应变速率对峰值应变和峰值强度的影响最弱，而在-20℃～-30℃时最为显着。此外，应变速率对耗散能的影响在室温下显着，而在 -30°C 时最弱。(4) 随着应变速率的增加或冻融温度的降低，分形维数逐渐增加，表明冻融环境对饱和试样的损伤和断裂程度有增加作用。我们的研究成果可为寒冷地区岩石工程的动力防灾和结构设计提供极其重要的理论依据。