Experimental study on water and heat migration of unsaturated loess under high temperatures

The strength of loess increases greatly with the decrease of water content. The high-temperature drainage method has broad application prospects for loess reinforcement, so it is significant to study the water and heat transfer of unsaturated soils under high temperatures. A water and heat transfer device allowing the action of high temperatures is developed to test the water and temperature fields of loess with specific initial water content under the action of a high-temperature heat source. The test results show that the high temperature has a significant driving effect on water compared with the normal temperature heat source. When the hot-end temperature exceeds 100℃, the water of soils close to the hot source is rapidly driven away at the beginning of the tests, which is caused by the significant increase of gaseous water migration due to the gas-liquid phase change. The distribution curves of water content gradually evolve from a peak type to a unidirectional increase one of the water content. Water migration fluxes significantly increase with heating source temperature. A high-temperature water and heat transfer model is established, and its accuracy is verified through the trial calculation. The comprehensive influence mechanism of high temperature and water content on water migration is analyzed based on the calculated results. The high-temperature water migration characteristics are divided into three intervals: Ⅰ(low water content interval), the water migration flux curve with water content shows a peak curve, and water migrates mainly in gaseous form. Ⅱ (medium water content interval), as the water content increases, the migration flux of gaseous water decreases while the migration flux of liquid water increases. Ⅲ (high water content interval), the temperature has a rare effect on the water migration. The findings may provide preliminary revelation on the water and heat migration characteristics of high-temperature unsaturated soils.