Moistening effects of high-fill embankment due to rainfall infiltration in loess gully region

Investigating the infiltration law and moistening deformation (MD) of high fill embankment (HFE) under rainfall infiltration (RI) conditions is of great significance for the exploration of the formation mechanism of post-construction settlement and the design of water drainage for high fill in the loess gully area. Based on a loess high fill project, the in-situ settlement monitoring of the fill area and the water-force characteristic experiments of unsaturated soil are carried out. The fluid-solid coupling numerical method is employed to study the infiltration law and MD characteristics of HFE under different rainfall types and compaction degrees. The results show that: (1) Because of the unevenness of compaction degree and rainfall type, the RI depth below the surface of HFE changes from 2.0 m to 7.0 m. (2) The MD ratio caused by heavy RI (storm, heavy rain) is 1.6%, which is greater than 1.2% of moderate rain and 0.3% of light rain. The MD ratios caused by heavy rainfall under different compaction degrees (λ=0.88, 0.93 and 0.98) are 1.8%, 1.5% and 1.3%, respectively. It indicates that the appropriate waterproofing and drainage measures are important to reduce the MD of HFE. (3) Heavy RI can cause excessive MD differences and shear strain mutations at the interface of the fill and the original foundation, which are the main sources of cracking and water damage at the junction of the fill and the original foundation.