Water infiltration and soil-water characteristics of compacted loess under applied vertical stress

Additional stress formed by post-construction buildings in loess-filling areas affects water infiltration in soil and causes soil deformation. To investigate this effect, under constant water head, vertical infiltration tests on compacted loess with two initial dry densities for different applied vertical stresses were developed using vertical stress-controllable one-dimensional soil columns. The time-history curves of vertical deformation, wetting front depth, cumulative infiltration depth, volumetric water content (VWC) and suction were measured, and the soil-water characteristic curves (SWCCs) were determined. The results showed that: (1) the infiltration ability of the soil column weakens with increasing applied vertical stress and initial dry density; (2) vertical deformation increases rapidly at first and then tends to be stable slowly at the consolidation and wetting-induced deformation stage, and is positively correlated with applied vertical stress and is negatively correlated with initial dry density. The stability time of wetting-induced deformation and the corresponding wetting front depth increase with the increase of applied vertical stress, while they decrease obviously when initial dry density increases; (3) the influence of applied vertical stress on soil-water characteristics in soil column with various initial dry densities is related to the deformation depth of soil column. The VG (Van Genuchten) model is suitable for fitting the SWCCs at different monitoring positions. A normalized SWCC model introducing the applied vertical stress was proposed for each initial dry density using the mathematical relationship between the fitting parameters and the applied vertical stress.