Experimental study on capillary water transport model based on AHFO technology

In order to verify the accuracy of commonly used capillary water transport models, several laboratory model tests are carried out based on the active heated fiber optic method (AHFO). During these tests, the soil moisture profiles determined by capillary force are measured using AHFO. Based on the experimental results, the characteristics and prediction accuracy of Green-Ampt and Terzaghi models are analyzed, so as to describe the moving rate of capillary water. In addition, the Lane and Peck models that predict the maximum capillary heights are evaluated as well. The results indicate that for sand, the capillary water rise process can be divided into two stages. During the first stage (first elapsed 50 hours), the predicted capillary water heights by the Green-Ampt and Terzaghi models are lower than the measured values collected by AHFO, and the accuracy of Terzaghi model is higher than that of the Green-Ampt model. During the second stage (after 50 hours), the predicted values are higher than the actual measured ones, and the Green-Ampt model has a higher accuracy. This accuracy change with time depends on model assumptions and physical properties of soils. The results also suggest that the error of the Peck model (2.60 cm) is lower than that of the Lane model (8.58 cm). The saturated hydrologic conductivity of the soils and the matric suction at the wetting front can be calculated by the Green-Ampt model. These discoveries provide basic data for selecting effective and high-precision models to reflect capillary rise in soils.