不同负温条件下冻土导热系数的理论模型和试验验证

THEORETICAL MODEL AND EXPERIMENTAL VERIFICATION ON THERMAL CONDUCTIVITY OF FROZEN SOIL UNDER DIFFERENT NEGATIVE TEMPERATURE CONDITIONS

基于饱和冻土的三相组成和导热系数量纲定义,将冻土简化为由土柱、液态水、冰柱组成的混合物,进而建立了冻土导热系数的几何模型。考虑实际冻土中三相组成的含量随温度变化而不断变化的事实,给出了随温度变化的水柱和冰柱体积计算与演变规律。在此基础上,利用并联体系导热效果的叠加原理,给出了随温度变化的冻土导热系数计算模型。基于热流传递过程中并联与串联同时进行的耦合特性,建立了考虑固-液界面的导热系数计算模型。将预测值与瞬态探针法的实测结果和Johansen法的计算结果对比后发现,该类计算方法能有效模拟不同负温条件下冻土的导热系数,并且具有概念清晰、方法简单等特点。

A geometric model of frozen soil thermal conductivity is established based on a simplified definition of frozen soil as a mixture of soil column, liquid water and ice column according to the three-phase composition and the definition of thermal conductivity of saturated frozen soil. The volume calculation and evolution law of water and ice column variation with temperature is established considering the fact that the contents of the three phases in the frozen soil change with the temperature. Based on the superposition principle of the thermal effect of the parallel system, the calculation model of frozen soil thermal conductivity is established. In view of the coupling characteristics of parallel connection and series connection in the heat transfer process, a calculation model of thermal conductivity considering the effect of solid-liquid interface is established. The comparisons among the calculation results, the experimental results with transient probe method and the results by Johansen＇s method indicate that those methods can effectively simulate the thermal conductivity of frozen soil under different negative temperature conditions with clear concepts and simple procedures.