Water and diesel percolation in unsaturated soil sand silt: an experimental approach

This work developed two-dimensional flow experiments with water and diesel SM soil, using an instrumented flow channel monitored by tensiometer and visual analysis. The soil was compacted with w=5% and rd =1.62 g.cm-3. The fluids migration occurred uniformly, both, in vertical and horizontal directions, with symmetrical spread of the infiltrating fronts. The ratio between the arrival time of the infiltrating fronts to the capillary fringe of diesel and water (td/tw) was 2.3; compatible with the ratio (2.16) between the liquid properties (ρ/μ/σ) for diesel and water. The behavior of the water and diesel isochrones were explained by the joint effect of gravity and friction on the liquids vertical flow, represented by the mobility (ρ/μ), and the lateral scattering by the capillarity effect, controlled by surface tension (s). The use of one-dimensional models to simulate advance of the two-dimensional infiltrating front resulted in considerable delay using the Brutsaert equation (1977), while Philip (1969) provided a considerable advance. The simulations using the Green Ampt model (1911) were close to the experimental data. However, the Philip model (1969) with the correction for the lateral scattering, resulted in better simulations, error of about 10%.