Flow visualization using transparent synthetic soils

Transparent materials including glass beads or quartz powder have been used to help in understanding flow processes through the soil. However, glass and quartz surrogates are limited by both their poor transparency and their inability to represent the geotechnical properties of soils. This paper demonstrates the feasibility of producing transparent soils made of amorphous silica gels or powders and liquids with matching refractive indices that can be used for modeling flow in soils, while representing the macroscopic geotechnical properties of a wide range of soils including sands and clays. Movement of a contaminant through soil was modeled. A clear pore fluid made of clear calcium bromide brine was used. A red dye was mixed in a mineral oil solution to represent contamination. The concentration of the oil-soluble dye solutions with known concentrations was simulated. These tests demonstrate that transparent synthetic soil can be used to visualize and non-intrusively measure pollutant transport in natural soils.