Freeze-thaw cycles will take place in the rock mass of natural state on the basis of changing in tem-perature and moisture. This will cause some unhealthy phenomenon such as micro-damage of rock,fragmentation of freeze-thaw and instability and failure and so on. That's the main weathering process of the rock mass of cold area in central and western regions. Freeze-thaw experimental study was implemented on different saturated water rate from Yungang Grottoes sandstone. Then the parameters including water absorption, longitudinal wave velocity and uniaxial compressive strength of rock mass can be obtained. The results showed that these parameters were not af-fected by the freeze-thaw cycles when the saturated water rate lower than 30%. These parameters begin changes be-cause of the freeze-thaw cycles when the saturated water rate between 30% and 70%. But these parameters have great changes when the saturated water rate more than 70%. So the saturated water rate of 70% was taken as the threshold value of freezing-thawing damage.%天然岩体在温度、水分变化的基础上发生冻融循环,引起岩石微观损伤、冻融碎裂以及破坏失稳等劣化现象,是中西部寒冷地区岩体的主要风化过程.将取自云冈石窟砂岩分成干燥组、饱水组、饱和度对比组进行冻融试验研究,得到试验前后云冈石窟砂岩吸水率、纵波波速、单轴抗压强度等变化参数.结果表明:砂岩饱和度<30%时,变化参数基本不受冻融作用影响;砂岩饱和度为30% ~70%时,变化参数开始受冻融作用影响;砂岩饱和度>70%时,变化参数出现突变现象.定义饱和S=70%为云冈石窟砂岩冻融损伤的"阈值".
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