冻土水分迁移机理研究:评述与展望

Study on the mechanism of moisture migration in freezing soils:review and prospect

土冻结过程中的水分迁移、积聚是冻害形成的关键环节,至今仍是冻土物理学研究的前沿和重要课题。二十世纪七八十年代冻土水分迁移研究黄金时代以后,长期未有经典理论和科学认知的重大突破,冻土水分迁移中涉及的许多机理性问题和关键瓶颈难题至今仍不能准确回答,尚存在很多争议和认识上的不足,现有研究成果在实际工程中的应用并不令人完全满意。因其性质的易变性、微观性和突变性,冻结相变区(冻结缘)仍是冻土水热输运研究中的一个“黑箱”。研究评述了冻土水分迁移驱动力与迁移过程相关研究的发展历程、主要研究进展与现状;分析了孔隙水压力、土水势驱动冻土水分迁移的物理原理和基本规律,综述了孔隙水压力、土水势的理论表征与试验测试等方面的最新进展、认知现状与主要科学问题;分析了三种流行的冻土水分迁移理论,即毛细水迁移理论、薄膜水迁移理论和水汽迁移理论;总结了制约冻土水分迁移科学认知突破的关键瓶颈难题,展望了未来研究的重点和方向。认为未来的研究应加强仪器设备的改进、研发与新技术引入,重点关注冻土水分迁移驱动力的物理本质和精准监测,强化冻土水分迁移的微观过程及机制认识,需从非平衡态热力学的视角关注热质输运与冰-水相变过程,注重工程化冻土多物理场模型的开发与自主开源计算平台的构建。本文旨在系统梳理冻土水分迁移机理的研究历史与现状,总结概述冻土水分迁移研究在新思想、新理论、新方法和新技术等方面的最新研究动态,凝练指出亟待解决的前沿科学问题和未来研究的重点,促进冻土热质输运基础理论的发展与完善,更好地服务于寒区工程冻融灾害和环境问题的解决。

The migration and accumulation of water during soil freezing,a crucial step of frost damage,has always been a frontier and important topic in the research of frozen soil physics.Since the golden age of water migration research for frozen soil in the 1970s and 1980s,there has been no major breakthrough in classical theory and scientific cognition.Many mechanical problems and key bottleneck problems involved in water migration in freezing soil still cannot be answered accurately.The damage and engineering problems related to frost heave haven’t been completely solved until now.Because of its variability,microcosm and mutation,the phase transition zone(frozen fringe)is still a“black box”in the study of water-heat transport in freezing soils.This paper reviews development history,main research progress and current situation of the research on the driving force and process of moisture migration in freezing soil,and then analyzes the physical principle and basic law of porewater pressure and soil-water potential related to moisture migration in freezing soil.We also summarize the latest progress and main scientific problems in the theoretical characterization and experimental tests of pore-water pressure and soil-water potential,and analyze three popular theories of the moisture migration,namely capillary-,film-,and vapor-water migration theory.This paper summarizes the key bottleneck problems that restrict the breakthrough of scientific cognition for moisture migration in freezing soil and looks forward to the focus and direction in future research.The research suggests that followings should be focused on in future:1)Strengthening the invention of instruments and the application of new technologies.2)Focusing on the physical essence and accurate dynamic monitoring of the driving force of moisture migration.3)Further understanding of the micro process and mechanism of the moisture migration.4)More attention should be paid to the process of heatmass transport and ice-water phase change from the perspective of non-equilibrium thermodynamics.5)The development of multi-physics coupling simulation and the construction of autonomous open-source computing platform.The purpose of this paper is to systematically review current situation and future research direction,and then promote the development and improvement of the basic theory in the heat-mass transport of freezing soil,and better serve the solution of freezing-thawing disasters and environmental problems in cold regions.