Relationship between temperature and water content of sodium saline soils without phase transformation
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摘要: 以硫酸盐渍土为研究对象,从理论上建立了冻结温度以上未相变含水率与温度的关系,并通过室内试验测试了硫酸盐土体及对应溶液中盐晶体初始析出温度和硫酸盐渍土未相变含水率在不同温度环境下的变化。从土体降温温度曲线、不同温度下核磁共振信号强度分析了温度对未相变含水率的影响。研究结果表明：在特定降温速率下,十水硫酸钠晶体析出存在滞后性,初始析出温度均低于其饱和浓度所对应的温度,并随着初始含盐量的减小,初始析出温度大幅度降低,且与土体比较,溶液中盐晶体易于析出;土体中十水硫酸钠晶体的析出造成含水率的减小明显大于溶液中晶体的析出引起的减小,且随着温度递降,未相变含水率递减;冻结温度以下,高含盐量的硫酸盐渍土未冻含水率与温度呈指数规律减小,-10℃以下,其含水率不再变化。对于低含盐量硫酸盐渍土,冻结温度以下其未冻含水率随温度降低同样按指数规律减小,且随着含盐量的增加,土体的含水率有所增加。Abstract: The relationship between water content without phase transformation of sodium sulfate saline soils and temperature is established above the freezing temperature of soils through theoretical analysis. In order to find the mechanism of the initial precipitation temperature of salt crystals in sodium sulfate saline soils and solution and change of water content under different temperature conditions, saline soil samples and solutions are tested in laboratory. By analyzing the cooling curves of soil samples and NMR single strength under different temperatures, the influence of temperature on water content without phase transformation is obtained. The research results show that, the precipitation of sodium sulfate decahydrate usually lags under specific cooling rate. Besides, the initial precipitation temperature is lower than the temperature of saturated solution. And also, the initial precipitation temperature decreases as the salt content of soil decreases. Meanwhile, the initial salt crystals are easier to form in solution than in soils. In addition, the decrease of water content in saline soils is greater than that in solution, and the water content without phase change decreases as the temperature decreases. The unfrozen water content of sodium sulfate saline soils with high salt content decreases exponentially, and the water content no longer changes when the temperature of soils is up to -10℃. For the sodium sulfate saline soils with low salt content, the unfrozen water content also decreases exponentially, and under the same temperature, the unfrozen water content of soils increases as the salt content increases.
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