饱和土水热耦合分离冰冻胀模型研究

针对饱和土一维冻结过程中的冻胀发展过程,在已有的描述透镜体生长过程的水热耦合模型的基础上,建立了水热耦合分离冰冻胀模型。利用固体表面水膜的热力学理论分析了冻土中未冻水膜在相界面上的平均分离压力,指出当该压力大于土层破坏的临界压力时,冰透镜体产生;以活动透镜体底端将土柱划分为主动区与被动区,主动区过程采用透镜体生长的水热耦合模型描述,而被动区为近似导热过程,由此建立了完整冻胀模型;提出了透镜体的分离冰生长方式,并与刚性冰生长方式进行了对比,阐述了本文模型与已有的各类模型之间的联系。采用有限容积法对模型进行了数值计算,与Konrad的3组试验进行了对比,结果表明模型很好地反应了土体冻结过程中温度场及冻胀的发展过程。

Separate ice frost heave model for coupled moisture and heat transfer in saturated soils

For the development of frost heave during 1-D freezing process of saturated soil, a separate ice frost heave model is established based on the ice lens growth model of coupled moisture and heat transfer. Average separate pressure of the unfrozen water film is analyzed by applying the thermodynamic theory for liquid layer near a substrate, and it is put forward that when this pressure exceeds the critical pressure of soil strength, new ice lens emerges. The soil structure is divided into active zone and passive zone by the interface of warm end of active lens. The process of active zone is described by the coupled moisture and heat transfer model of ice lens growth, while the passive zone approximately experience a heat conduction process, and then a frost heave model is established. A separate ice growth mode of ice lens is introduced, which is compared with the rigid ice growth mode of ice lens, and the connection between the proposed model and the existing models is expounded. Numerical simulation is conducted by using the finite volume method, and comparison is made with Konrad’s three tests. The numerical results of temperature field and frost heave are in general agreement with the experimental ones.