季冻区公路路基低液限黏土法向冻胀力试验

Experiment on Normal Frozen-heave Force of Low Liquid-limit Clay of Highway Roadbed in Seasonal Frost Region

首先,通过零位移平衡法的法向冻胀力试验,应用数理统计方法,分析了低液限黏土在冻结过程中产生的法向冻胀力与土体的温度、含水量、干密度、冻胀率等因素的关系,建立了法向冻胀力与冻胀率的线性回归方程,提出可以使用冻胀率对低液限黏土的法向冻胀力进行分级,并给出了适合路基填料的低液限黏土法向冻胀力分级标准;然后,通过加荷固结稳定后的冻胀试验,分析了上覆荷载对冻胀的影响;最后,将低液限黏土的法向冻胀力的分级标准与现有规范对比,得出各冻胀性类别的法向冻胀力界限值基本相同。结果表明:冻胀与法向冻胀力的产生是相铺相成的,施加微小的荷载,冻胀率就显著下降,同时,若允许有微小的变形时,法向冻胀力也就立刻松弛下来;然而无论预施荷载还是控制零位移时施加荷载并不影响冻胀现象发生。

The relationships between the normal frozen-heave force produced in the frozen-heave process of low liquid-limit clay and the factors, such as clay temperature, water content, dry density and frozen-heave ratio, were analyzed based on the normal frozen-heave force experiment of zero displacement balance method and numerical statistics method. The linear regression equation between the normal frozen-heave force and frozen-heave ratio was established. The classification of the normal frozen-heave force of low liquid-limit clay by frozen-heave ratio was proposed, and the classification standard of the normal frozen-heave force of low liquid-limit clay that fits for roadbed filling was given. Based on the frozen-heave test under load after consolidation, the influence of load on frozen-heave was analyzed. Lastly, by comparing the classification standard of the normal frozen-heave force of low liquid-limit clay with present criterion, it was concluded that the limit values of all kinds of normal frozen-heave forces are almost the same. The results show that frozen-heave and normal frozen-heave forces supplement each other; increasing tiny load can lead to frozen-heave ratio decrease significantly; at the same time, the normal frozen-heave force immediately shows looseness when allowing small deformation. However, both pre-increasing load and increasing load when controlling displacement will not affect the occurrence of frozen-heave phenomenon.