土体导热系数的评价与计算

A Calculation Method of Thermal Conductivity of Soils

土体的导热系数是土木工程热工计算的重要参数 .土体的多孔介质性质决定了土体的导热性质与干土、气体及孔隙充填物 (水 )的含量有密切关系 .实验测试结果表明 ,土体不论处于冻结还是融化状态 ,其导热系数均随干容重以及含水量的增加而增大 .采用土体的物理性质指标 ,对土体的导热系数进行了分析 ,给出土体导热系数较为方便的计算方法 ,有利于工程设计计算参数的选取 ,同时与实验测试结果对比 。

Thermal conductivity of frozen soil is an important index for analyzing the thermal state of frozen soil under natural condition. Experimental studies show that water content, dry density and soil type etc. influence the thermal conductivity. The conductivity increases with dry density and water content increasing. For a new frozen soil engineering, a great deal of tests should be conducted to determine the thermal conductivity of soil in thawed and frozen states, especially for a large permafrost engineering, such as railway and road line. So it is useful to devise a simple method to calculate the thermal conductivity in order to save test numbers and cost. In this paper a method for easily calculating the thermal conductivity is given for different water contents and dry densities.A shape function, expressed with a saturation degree, is introduced in the calculating method for soils in unfrozen and frozen states. At the same time, dry density, saturation degree, equivalent thermal conductivity of soils which is obtained with high dry density without water, thermal conductivities of water (in unfrozen state or ice in frozen state) and gas, are considered in the method. The calculated values of thermal conductivities of frozen and unfrozen soils by the formula suggested in the paper are well consistent with experimental data, not only for changing water content but also for changing dry density. The formula for soils in unfrozen and frozen states is very easy to operate.