Freeze-thaw has great deterioration effect on rock mechanical performance, which strongly affect the stability of rock masses engineering. Meanwhile, natural fractures in real rocks are ubiquitous with considerable variations in size, number, and orientation, which further accelerate the risk of geological disasters. In this study, the microstructure changes of specimens induced by cyclic freeze-thaw were measured using nuclear magnetic resonance (NMR) technique. Dynamic fracture tests were performed using single cleavage triangle (SCT) red sandstone specimens. Crack propagation gauges (CPGs) were applied to determine the crack velocity. Meanwhile, the microstructure of the fracture surface was obtained with the aid of scanning electron microscope (SEM). The results show that the cyclic freeze-thaw plays an important part in rock dynamic fracture behavior. The porosity and crack velocity increase with freeze-thaw cycles, whereas the crack initiation time and dynamic fracture toughness decrease with freeze-thaw cycles. Sandstone has three pore types and is susceptible to the freeze-thaw weathering. The fracture surface of specimen without freeze-thaw is smooth and the fracture mode is transgranular. With the rise of freeze-thaw cycles, the fracture surface becomes rougher, indicating that intergranular fracture plays a dominant role in sandstone failure.

冻融对岩石力学性能有很大的劣化作用，强烈影响岩体工程的稳定性。同时，真实岩石中的天然裂缝无处不在，其大小、数量和方向变化很大，进一步加速了地质灾害的风险。在这项研究中，使用核磁共振 (NMR) 技术测量了由循环冻融引起的试样的微观结构变化。使用单解理三角形 (SCT) 红砂岩标本进行动态断裂试验。裂纹扩展仪 (CPG) 用于确定裂纹速度。同时，借助扫描电子显微镜（SEM）获得断口的微观结构。结果表明，循环冻融在岩石动态断裂行为中起重要作用。孔隙率和裂纹速度随着冻融循环而增加，而裂纹萌生时间和动态断裂韧性随着冻融循环而降低。砂岩具有三种孔隙类型，易受冻融风化作用。未经冻融的试样断口光滑，断口为穿晶断口。随着冻融循环次数的增加，断裂面变得更加粗糙，表明砂岩破坏中晶间断裂起主导作用。砂岩具有三种孔隙类型，易受冻融风化作用。未经冻融的试样断口光滑，断口为穿晶断口。随着冻融循环次数的增加，断裂面变得更加粗糙，表明砂岩破坏中晶间断裂起主导作用。砂岩具有三种孔隙类型，易受冻融风化作用。未经冻融的试样断口光滑，断口为穿晶断口。随着冻融循环次数的增加，断裂面变得更加粗糙，表明砂岩破坏中晶间断裂起主导作用。