Issues

The mixing of different sized soil particles is known to affect soil properties such as density, porosity, hydraulic conductivity, and soil water retention. Although the first two have been studied and are relatively well understood, there are few studies on water retention properties for mixtures. In this study, two sets of particles with a large contrast in their diameters were mixed at different fractions, and their water retention properties were measured in a systematic manner.

We present a physically based model for hysteretic soil hydraulic properties. It has the potential to relate processes occurring at the pore scale to observations in larger scale problems.

A new experimental setup was used to study solute transport in sand for unsaturated conditions at constant pressure head and water content. This allowed for measuring saturation-dependent dispersivity as a third material property next to water retention characteristic and hydraulic conductivity function. Dispersivity was found to increase nonlinearly with decreasing water content. A distinct jump in dispersivity at a critical water content could be attributed to the structure of the flow field within the pore network using X-ray computed tomography.

We investigated the potential of using three-dimensional printing and three-dimensional X-ray microtomography to create reprints of macropore networks of undisturbed soil for water and solute transport experiments.

The spatial variability of rainfall at the soil surface and tree roots in a coastal sand dune forest was investigated. Various scenario simulations were further conducted using calibrated HYDRUS models to assess the effects of these vegetation-related variability patterns on soil moisture dynamics and the water balance.

Grain shape may affect the permeability of the granular materials. We conducted a series of pore flow simulations focusing on the grain aspect ratio. We observed that the aspect ratio affects both the possible range of void ratios and the surface area of packed grains. As a result, the aspect ratio indirectly affects the permeability.