建立在寒区的岩土工程,其岩石的损伤劣化不仅受冻融风化作用,而且还受到开挖卸荷的影响.采用冻融循环试验和三轴卸荷试验相结合的方法,对砂岩同时受2种破坏作用的强度特性和损伤特性进行系统的分析.分析结果表明:随围压的增加,冻融循环下岩石的破坏特性由张拉破坏逐渐转变为剪切破坏特征,随着冻融次数的增加,岩样明显产生侧向膨胀,侧边中部明显向外凸出,并出现了不同级别的张裂纹、环向裂纹及许多岩粉和岩石碎块;对于三轴卸荷试验,岩样的峰值强度随着冻融次数的增加而降低;扩容应力随冻融次数增加呈指数下降关系;破坏围压与冻融次数呈二次函数关系;冻融损伤值随冻融次数增加呈线性增长,表明岩样的损伤受冻融的影响逐渐增大.研究成果可为寒区岩土工程设计和施工提供指导.%Geotechnical projects in cold regions suffer from both cyclic freezing-thawing and excavation unloading, giving rise to rock degradation. In this article, the strength characteristics and damage characteristics of sandstone subjected to both cyclic freezing-thawing and excavation unloading are analyzed systematically by freeze-thaw cycle test and triaxial unloading test. The results are concluded as follows:in freeze-thaw cycle test,the sandstone expe-rienced a stage from tension failure gradually to shear failure as confining pressure rises; as the freeze-thaw cycle proceeds,the sandstone witnessed an apparent lateral expansion in the middle, with different levels of tension cracks,circular cracks,rock powder and rock fragments;while in triaxial unloading test,as freezing-thawing pro-ceeds,the peak strength of sandstone reduces,and dilatancy stress declines in an exponential relation;destructive confining pressure is in a quadratic functional relation with cycle number;moreover,the freeze-thaw damage value increases linearly with the number of freeze-thaw cycles,indicating that the effect of cyclic freezing and thawing in-tensifies gradually.
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