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冻土作为地质体存在在宇宙中,融化和冻结过程极为复杂:一方面它接受太阳及宇宙的热辐射,也接受来自地球内部的热能,还与近地层的大气进行热量交换和质量交换(水分的蒸发、凝结及降水);另一方面又有水的固-液相的转换,地下水渗流过程的对流换热,以及气态、液态水分在温差、密度差和毛细吸附作用下的重分布。当冻土表面有耐寒植被复盖时,还有生物化学过程的水-热作用参与等。即使按照冻土学的古典理论,把融冻过程中的冻土体看作是静态的,即仅仅是固-液相的转换,仍然不能得到封闭的分析解。若在人为作用下,比如修筑路堤,开挖基槽等使上部边界的几何形状有了凹凸时,所得到的计算公式近似程度就更差了。
Permafrost exists as a geological body in the universe. The process of melting and freezing is extremely complex. On the one hand, it receives heat radiation from the sun and the universe, it also receives thermal energy from inside the earth, and exchanges heat and mass exchanges with the atmosphere in the near-surface layer. Evaporation, condensation and precipitation); on the other hand, the solid-liquid phase conversion of water, the convection heat transfer in the groundwater seepage process, and the redistribution of gaseous and liquid water under temperature differences, density differences, and capillary adsorption. When covered with cold-resistant vegetation on the surface of the frozen soil, there is the participation of the hydro-thermal effect of the biochemical process. Even according to the classical theory of frozen soil, the frozen soil in the freezing process is regarded as static, that is, only the solid-liquid phase transition, and still cannot obtain a closed analytical solution. If artificial effects, such as the construction of embankment, excavation of the base trough, etc., make the geometry of the upper boundary concave and convex, the approximate degree of the calculated formula is even worse.