打开文本图片集
摘 要：冻土是一种特殊的土体，其性质与一般土体有较大差异。冻土中水分的含量与存在形式影响着冻土的各项性能。一直以来，冻土研究都是热点问题，由于试验手段的限制，对于冻土的分析以宏观研究较多。文中利用低场核磁共振孔隙分析仪，通过核磁信号的比值，计算各个温度点下未冻水质量含水率，绘制温度-含水率的函数曲线，结合不同条件试样的孔隙半径分布，揭示孔隙对未冻水含量的影响规律，并且探究不同初始含水率对曲线拐点的影响。试验结果表明，粉土、砂土和黏土土样冻结过程经历3个阶段：第Ⅰ阶段为过冷段，第Ⅱ阶段为迅速下降段，第Ⅲ阶段为稳定阶段;同种土质不同含水率的土样，降温过程发生冻结的拐点温度略有不同，但是差别较小;孔径分布越大，其冻结温度越低;未冻水含量与土体配合比关联较低，较多取决于土体本身的孔隙结构。
关键词：核磁共振;孔径分布;未冻水含量;冻土
中图分类号：TU 432
文献标志码：A
Experimental study on the unfrozen water content
and pore size distribution of frozen soil
KOU Jing-yuan1，2，TENG Ji-dong1，2，ZHANG Sheng1，2
（1.Department of Geotechnical Engineering，Central South University，Changsha 410075，China;
2.National Engineering Laboratory for High Speed Railway Construction，Changsha 410075，China）Abstract：
As a type of special soil，frozen soil is quite different with general soil.Frozen soil water content and form affect the various properties of frozen soil.At present，the study of frozen soil is a hot issue.Based on the limitations of experimental methods，macroscopic research on frozen soil is more.In this paper，low-field nuclear magnetic resonance pore analyzer was used to calculate the water content of unfrozen water at various temperature points by the ratio of nuclear magnetic signals.The function curve of temperature and water content was plotted.Combined with the pore radius distribution of the different conditions of sample，the effect of pore distribution on unfrozen water content was revealed，and the influence of different initial moisture content on
curve inflection point was probed.The results show that the freezing process of silt，sand and clay soil samples goes through three stages：the first stage is the supercooling stage，the second stage is the rapid descending stage and the third stage is the stabilization stage.For the same soil with different water content soil samples，the point of inflection temperature
in the cooling process of freezing is slightly different，but the different is small;the larger pore distribution，the lower the freezing temperature.The relationship between unfrozen water content and mix proportion is lower，more depending on the pore structure of the soil.
Key words：nuclear magnetic resonance;pore radius distribution;unfrozen water content;frozen soil
0 引 言
凍土是一种特殊的土体，其成份、组构、热物理及物理力学性质与一般土体均有不同。工程建设的过程中，会改变冻土的温度状况，影响冻土的含冰量和未冻水含量，进而影响冻土的力学特性。所以研究冻土随温度改变其未冻水含量的变化在冻土研究中显得尤为必要。冻土是由未冻水、固态冰、气态水和土骨架组成对温度十分敏感的复杂多项体系，水和冰的含量对冻土体的热学和力学物理性质有重要的影响，是进行冻土热工计算的必需指标[1-4]。
