寒区岩体由于反复冻融导致的变形破坏是当前亟待研究和解决的前沿课题。为研究裂隙岩体的冻融损伤特性,针对不同裂隙倾角的双裂隙灰岩开展冻融循环及单轴压缩试验,得到相应的应力-应变曲线及宏观破坏特征,并采用扫描电镜分析破坏面的微观结构特征。试验结果表明:双裂隙灰岩呈明显脆性破坏,其峰值应力、弹性模量均随裂隙倾角的增大而增大,随冻融循环次数的增加而减小。峰值应变随裂隙倾角、冻融循环次数的增加而增长。宏观破坏模式主要以裂纹模式为主,片落模式为辅,破坏面与预制裂隙有关,多为张拉裂纹。裂隙倾角＜90°时,贯穿裂纹经过双裂隙；裂隙倾角为90°时,贯穿裂纹仅经过预制裂隙①,片落模式仅出现在裂隙倾角＜90°的条件下。预制裂隙对破坏面的微观结构特征无明显影响,微观微裂纹平均长度、累计长度和平均宽度都随冻融循环次数增加而增大。裂隙倾角的增大抑制了冻融循环带来的损伤,提高了岩体耐久性。研究成果可为寒区矿山工程开采提供重要参考价值。

The deformation and damage to cold-region rock masses caused by repeated freeze-thaw cycles constitute a pressing forefront issue in need of immediate research and resolution. To investigate the freeze-thaw damage characteristics of fractured rock formations, freeze-thaw cycling and uniaxial compression tests were conducted on bifurcated gray limestone, varying the fracture angles. These experiments yielded the corresponding stress-strain curves and macroscopic failure features, with the utilization of scanning electron microscopy to analyze the fine structural attributes of the fractured surfaces.The experimental results reveal that bifurcated gray limestone exhibits pronounced brittle failure characteristics. Both peak stress and elastic modulus increase with the enlargement of fracture angles but decrease with an increase in the number of freeze-thaw cycles. Peak strain increases with the growth of fracture angles and the frequency of freeze-thaw cycles. The predominant macroscopic failure mode primarily entails a cracking pattern, with spalling as a secondary mode. The failure surfaces are closely associated with pre-existing fractures, primarily manifesting as tensile cracks. When the fracture angle is less than 90°, penetrating fractures traverse both pre-existing fractures, whereas at a fracture angle of 90°, the penetrating fractures exclusively follow the pre-existing fracture ①. Notably, the spalling mode exclusively manifests when the fracture angle is less than 90°. Importantly, pre-existing fractures exert minimal influence on the fine structural characteristics of the fracture surfaces. Nevertheless, microscopic crack attributes, including average length, cumulative length, and average width, increase with each successive freeze-thaw cycle. The enlargement of fracture angles serves to mitigate the damage induced by freeze-thaw cycling, thereby enhancing the overall durability of the rock mass. The research outcomes provide significant reference value for cold-region mining engineering operations.

国家重点研发计划(编号:2019YFC1803502)；国家重点研发计划(编号:2021YFC3001303)