Abstract: Water and salt cycling is a significant factor contributing to the gradual deterioration of rammed earth sites. To investigate the impact of size on the distribution characteristics of water and salt transport in rammed earth, five groups of cubic rammed earth samples with 0.3% salt content and varying side lengths (50, 100, 200, 500 mm, and 900 mm) were prepared. These samples were subjected to a natural water loss test in an indoor environment with a temperature ranging from 10–27 ℃ and a relative humidity of 20%−50%. Throughout the water loss period, borehole sampling was conducted to measure the moisture content and salt distribution from the surface to the internal soil of the rammed earth samples. The analysis focused on the water and salt transport characteristics and the size effects of rammed earth of different sizes. The test results revealed that the water loss period and the salt enrichment of the surface soil increased with the size of the samples, while the water loss rate decreased with the sample size. The water loss period of rammed earth samples of different sizes was categorized into three stages: rapid water loss, slow water loss, and stable water loss, with water and salt transport predominantly occurring during the rapid water loss stage. Throughout the water loss process, salt was transported to the sample’s surface layer along with the water, resulting in an increase in the salt content of the surface soil and a decrease in the internal soil’s salt content. This led to the gradual concentration and enrichment of salt in the surface soil. This study provides valuable theoretical support for indoor small block experiments, full-size simulating experiments, and field observation experiments in rammed earth sites.

Key words: rammed earth site, water and salt transport, water loss, salt content, moisture content, period, size effect