Research on Law of Water, Heat and Salt Movement in Earth Frost Heaving and Thaw Collapse

摘要

Frost heaving and thaw collapse are common natural phenomena. Frozen soil can be divided into permafrost and seasonally frozen ground. Total frozen area accounts for 75% of our territory area. So the frozen soil is considered to be valuable land natural resource. The frozen soil is a kind of composite material constituted of mineral particles, ice crystal, unfrozen water and air. The frozen soil shows up notably different physical property comparing with common earth for the existing of bonding ice. The impact of frost heaving and thaw collapse on earth is mainly presented in the movement of heat, water and salt. The research on the law of water, heat and salt movement in the process of earth frost heaving and thaw collapse is the key to resolve engineering problems and to prevent frost damage. This paper analyzed the movement of water, heat and salt in the process of earth frost heaving and thaw collapse and deduced that the water moves to surface throughout and never moves downward for temperature gradients. The salt in the earth moves two times including undercover salt accumulation in the process of freezing and exploding salt accumulation in the process of thawing. The heat flux thawing earth transporting to freezing surface is smaller than the heat in the frozen layer in freezing period. The heat flux the internal layer captured from upper and lower layer speed up the frozen soil thawing in thawing period. This work accumulates experience and provides a good exploration to further study the interaction relationship among water, heat and salt, and also give a new idea to forecast and prevent frost freeze damage in cold regions.