土壤冻融过程中水流迁移特性及通量模拟

为研究季节性冻土在冻融过程中水热盐的运移规律,在野外开展了一维及二维冻土水热盐运移试验,并通过Br离子示踪法及建立冻土水盐通量计算模型对土壤冻融过程中水盐的通量变化特性进行了计算分析。基于Hangen-Poiseuille孔隙通量方程,耦合孔隙冰柱体对水力传导度的影响机理,提出了冻土水流通量模型。结果表明,冻结过程中,液态水在水势和温度梯度作用下在冻结锋处聚集,形成通量峰值,冻融过程中自地表和最大冻深位置分别向下和向上的融化过程中,一维与二维试验水流通量变化对比表明,冻融过程中水流通量受到中间层冻土和地下水顶托的影响。冻土通量模型能够有效地描述冻土中不同温度条件下水流通量特性,从微观的角度很好地解释了土壤冻结过程中冰水共存状态下土壤中水流通量变化规律。

Water movement in soil freezing and thawing cycles and flux simulation

One dimensional and two dimensional field experiments were conducted to investigate soil water flux in frozen soil, based on tracer concentration changes and water balance analysis. A capillary bundle model was developed to incorporate the Hangen-Poiseuille law into the flow analysis in frozen soil. The model demonstrated how the soil water flux changes as function of liquid soil water content and hydraulic conductivity. Results showed that the effect of water potential and temperature gradient caused liquid water to accumulate near the freezing front to form the maximum water flux. Water flux was influenced by the intermediate frozen soil layer blockage and groundwater movement during the thawing of soil from two directions: the surface downward and the bottom upward. The capillary bundle model well described water flow in the frozen soil under various temperature conditions and was a useful tool to characterize water movement in the water-ice and soil system.