Estimating spatial and temporal water distribution in capillary rise zone of coarse-grained soils based on grain size distribution and unsaturated hydraulic conductivity

The spatial and temporal distribution of soil water content in the capillary rise zone characterizes fundamental physical behavior associated with capillary rise in soils. Accurate determination of water content distribution during capillary rise is highly necessary for soil mechanics and geotechnical applications. This paper proposed a straightforward and effective model to estimate the water content distribution along with capillary height and time. First, the drying soil–water characteristic curve (SWCC) is derived from the grain size distribution using the scaled MV-VG model. Next, the wetting SWCC is estimated by incorporating hysteresis effects, including contact angle hysteresis and the “ink-bottle” effect, into the drying SWCC to predict the water content distribution with respect to the capillary height. A theoretical solution for the maximum height of capillary rise is then proposed based on the calculated water content distribution. Finally, the model estimates the temporal distribution of water content using a modified Terzaghi's theory, incorporating the wetting unsaturated hydraulic conductivity derived from empirical and statistical models. Extensive comparisons with experimental data demonstrate the excellent accuracy and convenience of the model.