基于土水势动态监测的正冻土中水分迁移机理研究

项目名称： 基于土水势动态监测的正冻土中水分迁移机理研究

项目编号： No.40801026

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 能源与动力工程

项目作者： 温智

作者单位： 中国科学院寒区旱区环境与工程研究所

项目金额： 25万元

中文摘要： 土水势是冻土水分迁移研究中的关键参数之一，土水势通过影响冻结点控制冻土的未冻水含量。以往由于测试技术的限制，冻土土水势很难测定，制约了冻土水分迁移研究中许多机理性问题的准确回答。本研究通过室内试验的方法，利用新近推出的适用于负温冻结土环境的高精度基质势传感器、核磁共振装置和热敏电阻，直接测量土冻结过程中土水势和温度的动态变化，证实了冻土土水势控制冻土水分迁移方向和迁移量，即可用冻土土水势来描述冻土中的水分迁移过程；研究了降雨控制路基表层活动层水热过程，路基表层土体含水量变化和降雨过程有明显的相关关系，降雨通过影响地表能量平衡和改变土壤热物理性质的方式而影响活动层的水热过程。建立青藏粉质粘土土水势驱动水分迁移的理论模型。 基于现场监测水热过程资料和正冻土中水分迁移试验结果，建立了正冻土中水热耦合模型，并针对青藏高原典型普通冻土路基进行了算例分析。路侧积水条件下，会在冻土路基下活动层内形成可观的水分渗流迁移过程。伴随着路基水分运移，会在冻土路基下活动层内形成明显的热量迁移过程。路侧积水对冻土路基造成了明显的热影响和热侵蚀，导致积水侧路基融化深度加大和多年冻土的退化加剧。

中文关键词： 正冻土；未冻水含量；土水势；青藏粘土；水分迁移

英文摘要： Soil matric potential controls the unfrozen water content in frozen soil by effecting the freezing point of the soil solution, which depends on several interrelated factors, including particle size, pore size distribution, the distribution and characteristics of particle surfaces, soil organic matter quality and quantity. Soil matric potential is relate to the moisture migration in frozen fringe, ice lens formation mechanism, and the relationship between temperature and pressure. However, limited by instrument and testing technology, soil matric potential of the frozen soils can not be directly measured before. The existing instrument such as tensiometer, can not be used to measure the matric potential of frozen soils due to the limitation of positive operating temperature. A new soil moisture content sensor coupled with a new matric potential sensor that can operate in the subfreezing environment were used to measure the moisture content and soil matric potential dynamics of Qinghai-Tibetan silty clay. The study confirmed the soil water potential of frozen soil controlled the migration direction and migration of frozen soil moisture and soil moisture in the migration process can be described by soil water potential. Field investigation show that rainfall controls the roadbed surface layer hydrothermal process. A theoretical model of the Qinghai-Tibet silty clay soil water potential-driven moisture migration was presented. Based on site monitoring of the hydrothermal process information and soil moisture migration test results, frozen water-heat coupling model was presented and a numerical example of the Tibetan Plateau ordinary subgrade was conducted. The results shows that the water conditions of road side will affect the water seepage and migration processes in the embankment. Along with the the roadbed moisture migration, heat migration process in the active layer occurred. the water migration results in the increase in thaw depth and accelerate permafrost degradation under the embankment.

英文关键词： freezing soil; Unfrozen water content; Soil matric potential; Qinghai-Tibetan silty clay; Moisture migration