Abstract: In order to study the law of frost heave deformation of tunnel surrounding rock in cold area in practical engineering, the comparative tests of frost heave deformation of saturated sandstone under closed and open unidirectional freezing conditions were carried out respectively. The law of frost heave deformation of saturated sandstone under different environmental conditions was studied and a comparative analysis was made. The test results show that the saturated sandstone presents uneven frost heave characteristics under closed and open unidirectional freezing conditions, and the change process of frost heave strain is the same in two groups of tests, but the frost heaving rate and strain value of each temperature gradient under closed condition are slightly higher than those under open condition. With the same temperature gradient, it is found that the uneven coefficient of frost heave under open condition is slightly smaller than that under closed condition, but the growth rate of uneven coefficient of frost heave with temperature gradient under open condition is faster than that under closed condition. The changes of temperature field in the two groups of tests are divided into three stages: rapid decline, slow decline and stability. The total deformation of the specimen in the freezing direction has three-stage characteristics. The first two stages of two groups of tests are similar, which are cold shrinkage and slow growth stages. But the third stage is rapid growth stage in the open condition, with a linear growth trend. In the closed condition, it enters the stable stage, and the deformation volume tends to be stable. Through the comparative test, it can be found that the specimen is in-situ frost heaving under the closed condition, and in-situ frost heaving first and then partial frost heaving due to the supplement of external water under the open condition.

Key words: tunnel engineering; closed and open conditions; saturated sandstone; unidirectional freezing; frost heave deformation comparison

摘要： 为了研究实际工程中寒区隧道围岩的冻胀变形规律，分别进行了封闭和开放的单向冻结条件下饱和砂岩冻胀变形的对比试验，研究饱和砂岩在不同环境工况下冻胀变形的规律并加以对比分析。试验表明：饱和砂岩在封闭和开放的单向冻结条件下呈现不均匀冻胀特性，两组试验的冻胀应变变化过程相同，但在各个温度梯度的封闭条件下冻胀速率和冻胀应变值略大于开放条件下冻胀速率和冻胀应变值；在相同温度梯度下发现开放条件的不均匀冻胀系数略小于封闭条件，但随温度梯度增长速率大于封闭条件；两组试验温度场变化都分为快速下降、缓慢下降、稳定3个阶段；试件冻结方向总变形具有3个阶段特征，前两个阶段两组试验类似，为冷缩和缓慢增长阶段，呈第三阶段开放条件下为快速增长阶段，呈线性增长趋势，封闭条件下进入稳定阶段，变形量趋于稳定；封闭条件下试件产生原位冻胀，开放条件下试件先产生原位冻胀，后由于外界水分的补充产生分凝冻胀。

关键词: 隧道工程；封闭和开放条件；饱和砂岩；单向冻结；冻胀变形对比