为探究寒区砂岩在冻融循环作用下的孔隙结构损伤特性，对经历不同冻融循环次数的红砂岩试样进行了核磁共振试验，并结合多重分形理论，探讨了冻融循环作用对红砂岩不同尺度下孔隙结构的演化规律。结果表明：冻融作用促进了红砂岩孔隙结构发育，未经冻融作用的红砂岩T₂谱曲线呈3峰分布，经历冻融作用的红砂岩T₂谱分布曲线出现了4个峰，反映了冻融过程中红砂岩的孔隙结构演化复杂；单重分形不能表征红砂岩微小孔隙结构特征，但红砂岩微小孔和中大孔均具有良好的多重分形特征；分形参量与孔隙度高度线性相关。微小孔中总体非均质性参数D（0） - D（1）和低概率参数D（- 10）-D（0）与孔隙度负相关，赫斯特指数H与孔隙度正相关；中大孔单重分形维数D₂与孔隙度负相关，D（0） - D（1）、D（- 10） - D（0）、H均与孔隙度正相关；利用多重分形分析了冻融红砂岩孔隙结构演化规律，为深入研究冻融红砂岩损伤破坏机理提供了理论依据。

In order to explore the pore structure damage characteristics of the sandstone in the cold region under the freeze-thaw cycle, the nuclear magnetic resonance(NMR) test was carried out on the red sandstone samples undergoing different freeze-thaw cycles. Combining the multifractal theory, the evolution law of the pore structure in red sandstone at different scales under freeze-thaw cycles was explored. The results show that the freezing and thawing promotes the development of pore structure of red sandstone. The T₂ spectrum of red sandstone without freeze and thaw shows 3 peaks, and 4 peaks appeared in the T₂ spectrum of freeze-thaw red sandstone. It reflects the complex pore structure evolution of red sandstone during freezing and thawing. Mono-fractal does not characterize the pore structure of red sandstone micro-pores. However, both the micro-pores and medium macro-pores of red sandstone have good multifractal characteristics. Multifractal parameters are highly linearly associated with porosity. In the micro-pores, mono-fractal dimension D₂ is negatively correlated with the porosity, the overall heterogeneity parameters D(0) - D(1) and low probability parameters D(- 10) - D(0) negatively correlated with porosity, the Hurst index H is positively correlated with porosity. In the macro-pores, D(0) - D(1), D(- 10) - D(0) and H are positively correlated with porosity. The evolution of freeze-thaw red sandstone is analyzed by multi-fractal, it provides a basis for further study of the damage mechanism of freezing-thawing red sandstone.