Experimental investigation of ultrasonic atomization for moisture preservation at Han Yangling earthen sites

Cracking and salt accumulation are common forms of degradation in earthen sites exposed to soil-air interactions.Maintaining a high relative humidity alone cannot fully prevent degradation in earthen sites, mainly because moisture migrates unidirectionally from the site to the surrounding air.To address this, the study proposes a novel conservation strategy: Creating a mist-like atmosphere on the earthen site's surface using ultrasonic atomization technology to generate near-saturated air containing micron-sized water droplets. This promotes the return migration of liquid water, thereby inhibiting degradation.To verify the method's effectiveness, an ultrasonic atomization moisture system was established in a simulated exhibition hall of an earthen site at the Han Yangling Museum in Xi'an, and experimental tests were conducted to assess its performance. The results show that after moisture treatment, the soil moisture content at the surface of the earthen site returned to near its pre-excavation level. Some cracks healed significantly, and the soluble salt content at the surface decreased, with no salt damage observed.Furthermore, the ultrasonic atomization method showed optimal moisture effects during the early stages of excavation, offering valuable practical insights for its application in earthen site conservation.