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冻结特征曲线(SFCC)是指冻土中温度和未冻水含量之间的关系,采用核磁共振系统和低温恒温冷浴获得了采用不同浓度Na Cl溶液饱和的黏土的冻结特征曲线。根据试验结果分析不同浓度的孔隙溶液对冻结特征的影响规律,结果表明:随着溶液浓度的增大,冻结特征曲线向上移动,也就是说在相同未冻水含量下,浓度越大,冻结温度越低。这主要是因为盐溶液引起了渗透势能,使得孔隙水中总势能降低,从而降低了孔隙水的冰点。在冻土中,孔隙水的冻结温度与能量状态有关,其中孔隙水的势能包括基质势能和渗透势能,而基质势能部分又分为毛细部分和吸附部分,渗透势能与孔隙溶液的浓度有关。当土体中未冻水含量较低时,主要是吸附效应在起作用。此时未冻水是以吸附膜的形式吸附在土颗粒的周围,将非饱和土的概念引入到冻土中,采用分子间作用力和吸附水膜厚度之间的关系,以描述处于吸附状态的冻结特征曲线。结合渗透势能来模拟不同浓度下的冻结特征曲线,与试验数据拟合结果较好。
The freezing characteristic curve (SFCC) is the relationship between temperature and unfrozen water content in frozen soil. The freezing curve of clay saturated with NaCl solution with different concentrations was obtained by using the NMR system and cryogenic thermostatic cold bath. According to the experimental results, the influence of different concentration of pore solution on the freezing characteristics was analyzed. The results show that with the increase of solution concentration, the freezing characteristic curve moves upward, that is to say, under the same unfrozen water content, Lower. This is mainly because the salt solution causes the potential energy of permeation, so that the total potential energy in the pore water is reduced, thereby reducing the freezing point of the pore water. In frozen soil, the freezing temperature of pore water is related to the state of energy. The potential energy of pore water includes the matrix potential energy and the potential energy of penetration, while the matrix potential energy fraction is divided into the capillary part and the adsorption part. The potential energy of the pore water is related to the concentration of the pore solution. When the content of unfrozen water in soil is low, the adsorption effect is mainly at work. At this time, the unfrozen water is adsorbed on the soil particles in the form of adsorption film. The concept of unsaturated soil is introduced into the frozen soil. The relationship between the intermolecular force and the thickness of the adsorbed water film is used to describe the state of adsorption Freezing characteristic curve. Combined with the potential energy to simulate the freezing curve under different concentrations, the fitting results with the experimental data are good.