含水率及温度影响非饱和土导热系数的试验研究

土体的导热系数是能源岩土工程设计与研究中重要的热物理参数。工程中土体常处于非饱和状态。非饱和土体的导热系数会影响地下结构物的力学性能、热交换效率以及整个热工结构的工作效率。为给能源岩土工程设计与研究提供可靠的热物理参数,通过室内单元试验测量了不同含水率和温度下砾砂、粉土和黏土的导热系数,研究这三种非饱和土体的导热系数与含水率、基质吸力和温度的关系。研究结果表明,三种非饱和土体的导热系数都随含水率的增加而增加,最后趋于稳定。砾砂导热系数增加的速率最快,粉土次之,黏土最小。相同含水率下,砾砂导热系数最大,粉土次之,黏土最小。粉土的导热系数与基质吸力密切相关,其关系曲线趋势近似土 水特征曲线。三种土体的导热系数均随温度的增加近似线性增加,但增加幅度仅为10^-3级别,可忽略其影响。

Experimental Study on Effects of Water Content and Temperature on Thermal Conductivity of Unsaturated Soils

The thermal conductivity is an important thermophysical parameter in geo-energy engineering design and research. Soils in engineering is usually in an unsaturated state. The thermal conductivity of unsaturated soils will affect the mechanical properties and the heat exchange efficiency of the underground structure, and further affect the working efficiency of the whole thermal structure. In order to provide reliable parameters for geo-energy design and research, the thermal conductivities of gravelly sand, silt and clay at different water contents and temperatures were measured by element tests to study the relationships of thermal conductivity with water content, matric suction and temperature of the three unsaturated soils. The results show that the thermal conductivities of the three unsaturated soils increase with the increase of water content and then tend to be stable. The increasing rate of thermal conductivity of gravelly sand is the largest, followed by silt and clay. With the same water content, the thermal conductivity of gravelly sand is the highest, followed by silt and clay. Matric suction affects the thermal conductivity of silt, and their relationship trend is similar to the soil-water characteristic curve. The thermal conductivities of the three soils increase linearly with temperature, but the increasing magnitude is only 10^-3. Thus temperature influence can be ignored.