非饱和土水汽迁移与相变:两类“锅盖效应”的试验研究

发布时间：2019-01-24 21:58

【摘要】："锅盖效应"定义为:不透水覆盖层下土体含水率大幅提高甚至饱和。最新的理论研究将"锅盖效应"分为两类,第一类由非饱和土内水气冷凝引起,第二类是冻结条件下由气态水迁移引起。为试验验证两类"锅盖效应",研究其内在机理,利用新研制的非饱和冻土水汽迁移试验仪,对不同初始含水率的试样开展不同温度条件的水汽迁移试验。试验结果表明:冻结和未冻结两种状态均能使钙质砂试样顶部含水率增加,但冻结状态下的增加幅度显著。冻结状态下,含水率峰值位置与冻结锋面大致相同,且初始含水率越大,试样顶部和冻结锋面处的含水率增加越显著,降温速率越小,气态水迁移越显著;初始含水率增加也能使未冻结状态下的钙质砂试样顶部含水率增加,并且温度梯度对气态水迁移有一定的抑制作用,温度梯度越小,抑制作用越明显。试验结果很好地验证了两类"锅盖效应"的理论。
[Abstract]:"pot cover effect" is defined as: the moisture content of soil under impermeable cover is greatly increased or even saturated. The "pot cover effect" is classified into two categories in the latest theoretical studies. The first is caused by the condensation of water and air in unsaturated soil, and the second is caused by the migration of gaseous water under the condition of freezing. In order to verify two kinds of "pot cover effect" and study its intrinsic mechanism, a new unsaturated frozen soil water vapor migration test instrument was developed to test the water vapor migration of samples with different initial moisture content under different temperature conditions. The experimental results show that both frozen and unfrozen state can increase the water content at the top of calcareous sand, but the increase in frozen state is significant. Under freezing condition, the peak position of moisture content is approximately the same as that of freezing front, and the higher the initial moisture content is, the more significant the water content at the top of the sample and the freezing front is, and the smaller the cooling rate is, the more significant the migration of gaseous water is. The increase of initial moisture content can also increase the water content at the top of calcareous sand without freezing, and the temperature gradient can inhibit the migration of gaseous water to some extent, the smaller the temperature gradient, the more obvious the inhibition effect is. The experimental results confirm the theory of two kinds of "pot cover effect".
【作者单位】：中南大学土木工程学院;中南大学高速铁路建造技术国家工程实验室;
【基金】：国家重点基础研究发展计划(“973”计划)项目(2014CB047001) 国家自然科学基金项目(51508578)
【分类号】：TU41

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