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基质势是驱动冻土中水分发生迁移的关键驱动力之一,但由于以往的技术限制,负温下土体的基质势难以被直接测量,冻土基质势相关问题成为冻土水热过程研究中的难题。利用可用于极端负温条件下的pF meter基质势传感器,针对青藏红黏土、兰州粉土以及张掖细砂这三种不同粒径级配的土体,分别从粒径大小和初始含水量的角度,通过室内试验,研究了土体冻结与融化过程中基质势、未冻水量以及温度三者之间动态变化的关系。结果表明:冻土中的冰晶体对基质势和未冻水量的影响类似于融土中的气体,而冰晶体的含量又与土体温度相关;由粒径级配决定的比表面积对冻土基质势存在着决定性的影响;此外,初始含水量的多少对冻土基质势也存在与融土类似的影响。研究成果揭示了负温冻土中未冻水的数量与能量状态随冻结与融化过程的变化关系,为研究冻土中水分在基质势驱动下的迁移过程提供了理论基础和试验支撑。
The matrix potential is one of the key driving forces driving the migration of moisture in the frozen soil. However, due to the technical limitations of the past, it is difficult to directly measure the matrix potential of the soil under negative temperature. In the puzzle. Using the pF meter matrix potential sensor which can be used under extreme minus temperature conditions, this paper aimed at the grading of three kinds of soil with different grain sizes, such as Qinghai-Tibet red clay, Lanzhou silt and Zhangye fine sand from the aspects of particle size and initial water content Through laboratory experiments, the relationship between the dynamic changes of matrix and unfrozen water and temperature in soil freezing and thawing was studied. The results show that the influence of ice crystals in frozen soil on the mass flux and unfrozen water is similar to that in the melt, and the ice crystal content is related to the soil temperature. The specific surface area There is a decisive influence on the matrix potential. In addition, the initial water content also has a similar effect on the soil matrix potential of the frozen earth. The research results reveal the relationship between the amount of unfrozen water and the energy state in the frozen soil under the influence of the freezing and thawing process, and provide the theoretical basis and experimental support for the study of the migration of moisture in the frozen soil driven by the stromal potential.