Coupled heat and moisture flow in unsaturated soils under opposing thermal and hydraulic gradients

Experimental studies of coupled heat and moisture flow induced in an unsaturated soil by simultaneously imposed temperature and hydraulic gradients, in opposite directions, are presented. This study was designed to provide information on the moisture and temperature distributions in relation to elapsed time and distance from the heat source. Tests were conducted on sand and buffer in the following order: a) buffer, one layer system, and b) sand and buffer, two layer system (in which buffer consists of silica sand and sodium bentonite in equal proportion). Materials were compacted to their maximum dry density and optimum water content. The experiments were performed with the application of external hydraulic and temperature gradients in opposite directions. The experimental results show that moisture flows from the hot and cold ends to the middle part of the soil column due to externally applied hydraulic and temperature gradients. They also indicate that the use of a sand layer between the buffer material and waste container reduces the shrinkage of the buffer material.