寒区非饱和土体混合态水分迁移研究进展

Research progress of mixed water transport in unsaturated soils of cold region

综合分析了冻土液态水和气态水迁移机制以及水热耦合数值模型,归纳了土水势理论和水汽迁移成冰理论的研究进展,综述了冻土传统水分迁移驱动力理论和水汽迁移驱动力理论,分析了工程地基土体增水机理,对水热力和水热汽耦合作用理论进行了总结分析,并对比了不同数值模型的特点。因冻土冰水相压力的不明确,Clapeyron方程在冻土中的适用性还需进一步探究;水汽遇冷冷凝作用和水汽蒸发凝结作用很好地解释了非饱和土体的增水机理;传统水分迁移理论多是基于液态水展开研究,忽略了水汽运移的影响,水汽迁移成冰理论很好地解释了水汽运移引起的工程冻害;水热力耦合迁移理论没有充分表征应力场的作用,不能完全揭示土体冻胀的形成和发展过程。

Considering that most projects in cold regions are located in arid or semi-arid regions,this paper comprehensively analyzes the migration mechanism of liquid water and gaseous water in the frozen soil and the model of hydrothermal coupling,in order to provide theoretical support for the study of the migration mechanism of mixed state water in frozen soil,as well as the prevention and control of engineering freezing damage.The research progress of soil water potential theory and vapor transfer-induced freezing theory are summarized,and at the same time,detailed reviews on the traditional moisture migration force theory of frozen soil and migration force theory of water vapor are analyzed.Then,a deeply analysis on the water increasing mechanism in the engineering foundation is conducted,and in addition,this study also summarizes coupled models of the water thermal force and water-vapor,with comparing the characteristics of different numerical model.According to the analysis,the following results can be obtained that considering that the concept of pressure of ice-water phase pressure is not clear,the applicability of Clapeyron equation in the frozen soil needs to be further evaluated.The traditional water migration theory is based on liquid water and ignores the influence of water vapor migration.The water accumulation mechanism of unsaturated soil is well explained by cold condensation and evaporation condensation of water vapor.Meanwhile,the theory of the vapor transfer-induced freezing can well explain the engineering freezing damage caused by the water vapor migration.Finally,the hydro-thermal coupling theory does not fully represent the action of stress field and cannot fully reveal the formation and development process of soil frost heave.