Experimental study of upward migration of heat and moisture in loess based on non-contact temperature and humidity field testing technology

Understanding and utilizing the laws of heat and moisture migration in loess under climate change is crucial for slope engineering safety and agricultural production. A custom-designed vertical temperature-controlled heat and moisture migration test device, coupled with non-contact continuous measurement technology for temperature and moisture fields, was used to perform heating tests with varying temperature levels and initial water content conditions at the bottom of loess samples. The study investigates the vertical heat and moisture migration in loess under the combined effects of thermal potential, gravitational potential, and matric potential. The results show that: (1) At heat source temperatures ranging from 45℃ to 75℃, the temperature field of the loess samples stabilizes within approximately 24 hours. (2) Between 0 and 40 cm in height, samples with higher heat source temperatures and initial water content exhibit larger stable temperatures and thermal gradients. (3) As the heating time increases, the vertical moisture content of the soil sample shows a significant peak in the height distribution curve, with the position of the peak gradually shifting upward and the peak magnitude progressively increasing. (4) The thermal potential plays a dominant role in the upward migration of moisture in loess, with higher temperatures significantly increasing the driving force for moisture movement. (5) The upward migration of water is most pronounced when the initial moisture content is moderate.