土体热传导性能及其热导率模型研究

为研究不同土体的热传导特性变化规律,利用热探针测试了南京地区典型土体在不同含水量和干密度状态下的热阻系数,分析了含水量、干密度、饱和度以及矿物成分等因素对土体热阻系数的影响,研究了不同状态下土体热导率的预测模型,提出了适用于不同地区土体热阻系数估算的修正系数.结果表明:南京地区典型土体的热阻系数随含水量和干密度增加而减小,当含水量超过一定范围后,热阻系数趋于稳定;热阻系数与饱和度之间的关系表现出与其含水量之间相似的变化规律;土颗粒的热传导特性由其矿物成分决定,石英含量对土颗粒热传导特性有着显著影响;提出了可用于非饱和土热导率估算的修正归一化模型,该模型对于粗粒土具有较高的预测精度,细粒土则需考虑区域差别进行修正.

Research of Soil Thermal Conduction Properties and Its Thermal Conductivity Model

To investigate the heat transfer characteristics of different soils, a non steady thermal probe technology was used to measure thermal resistivity of typical soils in Nanjing area with different moisture content and dry density. The effect of moisture content, dry density, saturation, mineral composition and other factors on thermal resistivity were studied and the generalized thermal conductivity prediction models for soils at different states were established. The correction factors for prediction model to estimate thermal resistivity of both Nanjing and India soils were proposed. The test results indicate that thermal resistivity of soil decreases with the increase of moisture content and dry density and trends to the constant value when moisture content exceeds a certain value. The relationship between thermal resistivity and saturation is similar to that of moisture content. Thermal conductivity of soil particle is determined by itsmineral composition and the fractions of quartz have a significant effect on the heat transfer characteristics of particles. Geometric mean method can be used to estimate the thermal conductivity of saturated soils. A modified normalized model for predicting thermal conductivity of unsaturated soils at unfrozen state is proposed, and the prediction results for sandy soil are of high accuracy, but for fine particle soils are needed to be adjusted for considering the difference in soil deposited areas.