脱湿过程中红黏土热导率的变化试验研究

自然状态下岩土体中的三相组成处于动态变化之中,对土体热传导性能的准确测试造成困难,通过热导率脱湿曲线(TCDC)可间接获取土体的传热性能。为此,以桂林红黏土为研究对象,采用压力板仪和KD2 Pro土壤热特性分析仪,研究了红黏土在脱湿过程中热导率的变化规律。试验结果表明:在进气值之前,土体饱和度不变,3种干密度的土体热导率都有小幅度增加,此阶段主要与吸力变化引起的土体密实度变化有关;当吸力超过进气值后,热导率随饱和度减小逐渐减小,此阶段含水率为影响热导率的主要因素。基于热导率试验结果,采用Lu模型和William模型对红黏土脱湿过程中热导率变化曲线进行拟合,整体上2模型对试验结果拟合较好,可以用于红黏土脱湿过程中热导率变化的模拟。

Experimental Study on Thermal Conductivity of Red Clay in Drying Process

The dynamic change in the three-phase composition of rock and soil in natural environment poses difficulty to the accurate test of thermal conductivity of soil. The heat transfer property of soil can be indirectly obtained through the thermal conductivity dryout curve (TCDC). In this research, the change rule of thermal conductivity of Guilin red clay in drying process was examined by using pressure plate and KD2 Pro soil thermal properties analyzer. Before the matric suction reached the air entry value, the saturation of soil remained unchanged, and the thermal conductivity of soil specimens with varied dry density increased slightly; in this stage, thermal conductivity was mainly related with the change of soil density caused by the change of suction. When matric suction exceeded the air entry value, the thermal conductivity gradually decreased with the reduction of saturation degree; at this stage, moisture content was the main factor affecting thermal conductivity. Based upon the experimental results, Lu's model and William's model were employed to fit the thermal conductivity curve of red clay in the drying process. Both models have good fitting results, hence can be used to simulate the change of thermal conductivity in red clay in drying process.