Experimental study on thermal moisture migration of unsaturated loess humidified by spherical steam source

The water-vapor-thermal coupling transport in unsaturated soils is a complex process affected by multiple factors. The experiment is designed to use the remolding unsaturated loess filling model, and the high-temperature steam with a certain pressure is ventilated in order to study the law of thermal mass migration in remolded unsaturated loess under the action of vapor pressure gradient, temperature gradient and water content gradient. Based on the boundary conditions of the model tests, a set of special solutions to the governing equation for heat-wet transport in unsaturated loess under humidification of spherical steam source are obtained. The results show that when the spherical steam sources diffuse in unsaturated loess, the migration range of water and temperature is similar to an ellipsoid. When the water vapor moves along the radial direction, the vapor pressure gradually dissipates, the migration rate decreases, and the temperature conduction rate decreases. When the vapor pressure is large, the humidification rate, range and degree will increase. In the effective humidification range, the moisture content of soils varies between 11% and 17%, which is close to the optimal moisture content of the soils, and the humidification effect is better. The heat transfer of high-temperature steam in the soils includes the heat transfer caused by the high-temperature steam and temperature gradient. The effective humidification range is mainly decided by the high-temperature steam heat transfer, and the temperature migration rate belongs to the rapid migration stage. The temperature migration outside the effective humidification range is mainly decided by the heat transfer caused by the temperature gradient, which belongs to the slow migration stage. The comparison between the measured and calculated values shows that the algebraic explicit analytical special solution can better reflect the variation law of soil temperature and moisture content in the experiment. The research results can provide a theoretical reference for the new technology of water-heat coupled migration and vapor humidification in unsaturated loess.