水蒸气增湿非饱和黄土热湿迁移规律研究

Study of thermal moisture migration of unsaturated loess with water vapor

温度梯度、含水率梯度和压力梯度对非饱和土体中的水热迁移有重要影响。用非饱和黄土填筑室内模型,通入0.10MPa高温水蒸气,研究蒸汽压梯度、温度梯度和含水率梯度耦合作用下的水热迁移规律。结果表明:在水蒸气迁移范围之内,土体的升温速率、增湿速率和增湿程度较大,以蒸汽传热和压力梯度驱动的水蒸气增湿为主。而在水蒸气未到位置,以温度梯度引起的热传导和含水率梯度与温度梯度耦合驱动的水热迁移为主;水蒸气迁移时,受土颗粒阻碍和蒸汽压消散的影响,土体升温速率、增湿速率和温度传导速率均随径向距离的增大而减小,且增湿速率小于升温速率;水蒸气增湿土体的最大含水率接近最优含水率,增湿效果较好,可有效提高一定范围内土体的压实性能;基于模型试验边界条件,确定含湿毛细多孔介质中二维热湿迁移方程的一组代数显式特解,并以20 cm测点为例,将温度和含水率实测值和计算值进行对比分析。研究结果可为非饱和黄土水-汽-热耦合传输规律和水蒸气增湿新技术研究提供理论支持。

Temperature gradient, moisture gradient and pressure gradient significantly affect hydrothermal migration in unsaturated soils. The unsaturated loess sample under 0.10 MPa of high-temperature water vapor is tested to study the hydrothermal migration under the gradients of steam pressure, temperature and moisture. The results show that the high rate of temperature rise, and water vapor humidification observed within the range of water vapor migration and the steam humidification are mainly driven by steam heat transfer and pressure gradient. In the region beyond water vapor migration, the heat conduction caused by temperature gradient and water migration driven by moisture gradient coupled with temperature gradient are the main factors. Under the influence of soil particle obstruction and steam pressure dissipation, the rate of soil heating, humidification and temperature diffusion decrease with the increase of radial distance, and the rate of humidification is less than temperature diffusion. The maximum moisture content of water vapor humidified soil is close to the optimal moisture content, and the humidifying effect is good, which can effectively improve the compaction performance of soil within a certain range. Based on the boundary conditions of the model test, a set of algebraic explicit special solutions to the two-dimensional heat-wet migration equation in a moist porous medium is determined. The measured and calculated values of temperature and water content are compared and analyzed at 20 cm measurement points. The results can provide theoretical support for the research on the transmission of water-vapor-thermal in unsaturated loess and the new technology of water vapor humidification.