Abstract: 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.

Key words: red clay, thermal conductivity, soil-water characteristic curve, thermal conductivity dryout curve, drying process