Pulsed NMR Measurements of Unfrozen Water Content in Partially Frozen Soil
Pulsed NMR Measurements of Unfrozen Water Content in Partially Frozen Soil
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DOI：
10.1061/(asce)cr.1943-5495.0000220
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发表时间：
2020-09-01
影响因子：
2
通讯作者：
Sugimoto, Mitsutaka
中科院分区：
文献类型：
--
作者：
Li, Zhiming;Chen, Jian;Sugimoto, Mitsutaka
未冻水是冻土的重要组成部分，决定了冻土的热、力学特性，并在冻融循环过程中对工程结构产生影响。本文利用脉冲核磁共振技术研究了不同初始含水量和干密度的粉质粘土、中砂和细砂土在冻融过程中未冻水的行为。基于毛管理论和Gibbs-Thomson方程，推导了一种估算冻结过程中未冻孔隙中未冻水含量的积分形式。然后，使用吸附的薄水膜的厚度和Clapeyron方程计算冻结孔隙中的未冻结水含量。根据相似理论建立数学物理模型，得到解冻过程中温度与未冻水含量的关系曲线。该模型进行了验证，使用实验数据和数据从以前的研究。未冻水含量是高度依赖于干密度和土壤类型，所有的曲线在冻结和融化过程中表现出滞后，由于不同的孔隙水的热力学势。
Unfrozen water is a critical component of frozen soil that determines its thermal and mechanical behavior and affects engineering structures during freeze-thaw cycles. Here, pulsed nuclear magnetic resonance was used to investigate the behavior of unfrozen water in silty clay, medium sand, and fine sand soils with different initial water contents and dry densities during freezing and thawing. An integral form was derived based on the capillary theory and the Gibbs-Thomson equation to estimate the unfrozen water content in unfrozen pores during freezing. The unfrozen water content in frozen pores was then calculated using the thickness of an adsorbed thin water film and the Clapeyron equation. A mathematical physical model was established based on similarity theory to obtain curves relating the temperature and unfrozen water content during thawing. The model was validated using experimental data and data from previous studies. The unfrozen water content is highly dependent on the dry density and soil type; all curves showed hysteresis during freezing and thawing owing to the different thermodynamic potentials of pore water.