青藏粉质黏土冻融过程水热特征研究

土体在冻融过程中的水热特征对于冻胀及工程稳定性具有决定性作用。以青藏粉质黏土为例,采用时域反射法(TDR),测量并分析了不同初始含水率条件下的土样在冻融过程中的水热变化特征,对比了冻融过程中的水热变化及其差异性,采用Anderson等、徐敩祖等和Michalowski提出的以温度为变量的未冻水计算公式,分别计算了不同初始含水率土样在不同温度条件下的未冻水含量。结果表明:冻融过程的土样水分和土样中心温度随时间的变化均可分为三个比较明显的变化阶段,冻结过程和融化过程的变化特征略有不同,除了环境影响和探头自身因素外,我们将其归因于冻融过程的未冻水"滞后效应"。在快速冻融过程中,未冻水含量随温度的变化则表现出渐变的特征。通过对比三种典型未冻水含量的计算方法发现,通过拟合得到的方程计算结果的正确性较高。

Study of the water and thermal features of Qinghai-Tibet silty clay during freezing and thawing

During freezing and thawing,the change features of water and heat significantly affect the frost heave and thermal stability of engineering in cold regions.In this paper,Qinghai-Tibet silty clay was selected to measure the changes of water content and temperature through time domain reflectometry method (TDR) with various initial water content,the differences in the change in water content and temperature during freezing and thawing have been compared.Furthermore,three calculation models were used to calculate the unfrozen water contents of soil samples with various initial water content at the temperature below freeze point.The results showed that the changes of water content and temperature can be divided into three stages according to the change features.The features in freezing is little different from those in the thawing.Except for the environmental factors and probe defect influence,these differences may be ascribed to hysteretic effect of unfrozen water during freezing and thawing.In the process of rapid freezing and thawing,the change trend of unfrozen water content with temperature exhibits a gradual change.Comparison of the three calculation models on unfrozen water content shows that the calculation results of fitted equation has higher validity.