Abstract: Freeze-thaw cycles (FTCs) exert a significant impact on the stability and safety of engineering during the construction, operation and maintenance in clod regions. To investigate the impact of FTCs on the hydro-thermal deformation interaction within gravel interlayer structures, silty clay and gravel were selected to construct the gravel interlayer structure. By monitoring the changes in soil temperature, unfrozen water volume, soil pressure, and displacement deformation of the specimens during the freeze-thaw cycle, the influence rule of the freeze-thaw cycle on the gravel interlayer structure was revealed, and three kinds of machine learning algorithms were employed to develop predictive models for vertical displacement in gravel interlayer structures, respectively. The test results reveal that notable temperature fluctuations occur within the gravel interlayer during the FTCs, and the gravel interlayer has a certain heat insulation effect on the lower soil. Additionally, under the FTCs, both the silty clay samples and the gravel interlayer samples undergo internal moisture migration and redistribution. However, the unfrozen water content in the gravel interlayer structure remains relatively stable. The gravel interlayer structure is less prone to significant deformation during the FTCs, whereas the displacement deformation and frost heaving/thaw settlement rates of silty clay samples are both higher than those of gravel interlayer samples. During a single FTC, the soil pressure of the silty clay sample initially decreases and then increases, while the soil pressure variation in the gravel interlayer exhibits two distinct peaks. The XGBoost model can effectively predict the vertical displacement of the gravel interlayer structure, with a correlation coefficient (R2) between the predicted and measured values greater than 0.93.

Key words: geotechnical engineering; freeze-thaw cycle; silty clay; gravel; unfrozen water; deformation

摘要： 在寒区工程的建设和运维过程中，冻融循环对工程的稳定性和安全性有显著影响。为探究冻融循环作用对碎石夹层结构的水-热-变形相互作用过程的影响，选用粉质黏土和碎石构建碎石夹层结构，通过监测冻融循环过程中试样的土体温度、体积未冻水、土压力和位移的变化，揭示冻融循环作用对碎石夹层结构的影响规律，并采用3种机器学习算法分别建立碎石夹层结构的竖向位移预测模型。试验结果表明：冻融循环过程中，碎石夹层部分温度波动明显，碎石夹层对下部土体有一定的隔热保温作用；冻融循环作用下粉质黏土试样和碎石夹层试样内部的水分均发生了迁移和重分布，其中碎石夹层结构的体积未冻水含量变化较为稳定；碎石夹层结构在冻融循环过程中不易发生大幅度的变形，粉质黏土试样的位移变形、冻胀/融沉率均高于碎石夹层试样；单次冻融循环过程中粉质黏土试样的土压力先减小后增大，碎石夹层的土压力变化出现了两次较为明显的波峰；XGBoost模型可有效预测碎石夹层结构的竖向位移，预测值与实测值的相关系数R2大于0.93。

关键词: 岩土工程；冻融循环；粉质黏土；碎石；未冻水；变形