冻融作用对土工程性质影响的研究现状

STATE-OF-THE-ART OF INFLUENCE OF FREEZE-THAW ON ENGINEERING PROPERTIES OF SOILS

冻融过程中土结构受冷生作用的影响,可导致土的工程性质发生变化。在冻土地区进行路堑开挖、新消边坡的加固和路基修建时,由于新近暴露的土受到冻融风化作用,在相关的变形和稳定性分析中,选择土性参数时必须考虑土工程性质的变化。在查阅大量文献的基础上,从试验仪器和研究方法、冻融作用下土的物理性质和力学性质的变化及其机理等几个方面,对土的工程性质受冻融循环影响而改变的研究现状进行了总结和分析,列出了典型的研究成果。文献研究表明,土经过冻融后,渗透性会增大;松散土和密实土的密度具有不同的变化趋势;原状超固结土的结构性受到破坏,因而三轴试验的应力应变曲线峰值受到削弱,一维压缩试验中表现为前期固结压力降低;强度的变化则有诸多不同的试验结果。针对目前的研究现状并根据作者的相关工作,提出了进一步研究的思路。

It has become a common understanding that frost action is a kind of weathering process, which considerably changes engineering properties of soils due to cryogenical actions. Soils newly exposed to freeze-thaw in cold regions tend to change their properties. Therefore, care must be taken with respect to the freeze-thaw induced influence on stability and deformation of engineering constructions. With a view of the state-of-the-art, this paper reviews the general findings of the research on this topic on the basis of an extensive literature study. Technically, the following aspects of soil behavior regarding freeze-thaw are included： the means of investigation and testing techniques, physical and mechanical properties as well as mechanism analysis. Typical research results are taken from various resources and listed herein. The influences of freeze-thaw on soil properties can be summarized that, permeability of soils is generally increased despite of the change of density; densities of loose and dense soils are changed in the opposite way ; structure of undisturbed soils can be changed, as the results peak in the stress-strain curve is not as pronounced as that in the pre-freezing ones; strength change is not well in agreement from the previous studies. The authors＇comments on previous studies and ideas for further investigation with regard to particularly concerned aspects are given. It is suggested that the original state, such as stress state, density and preconsolidation ratios should be taken into consideration for a more systematic investigation. Meanwhile, the deformation versus time during freezing and thawing may serve as a sound proof of change in particle bondings.