Back-calculated soil-water characteristic curve from fluid flow data

The soil-water characteristic curve (SWCC) is a fundamental property of an unsaturated soil that is used to predict multiphase flow and transport through porous media. Direct measurement of the SWCC using conventional testing devices is time consuming. A methodology with which to estimate the SWCC is proposed in this paper based on the recorded data of transient fluid flow into soil during a 50 g centrifugal test. An inverse analysis was performed to fit the numerical simulation results, obtained using a finite element multiphase flow code NAPL simulator, to the centrifugal model test data. For the numerical simulations, several sets of representative SWCC parameters of the modeled soil were assumed. Based on an optimization scheme, the parameters that produced the best match between measured and simulated data were selected, and the SWCC for the soil was predicted. To validate the proposed method, the predicted SWCC was compared with that obtained via a conventional test. The comparison showed that the SWCC obtained via inverse analysis with a van Genuchten model parameter set of α=0.4m^-1 and η=3 compared relatively well to the measured one. Thus this new method, based on inverse analysis of the fluid flow data from centrifugal modeling, could be used as a reliable, indirect technique for predicting field SWCCs.