unsaturated hydraulic properties of gravels
Tetsu K. Tokunaga, Keith R. Olson, and Jiamin Wan
Contact: Tetsu Tokunaga, 510/486-7176, tktokunaga@lbl.gov
Research Objectives
Gravels can make up large fractions of the subsurface,
including vadose zones. The extensiveness of some gravel deposits
is evident from the fact that they serve as major aquifers that
supply groundwater for agricultural, industrial, and municipal use.
Because some gravel deposits do occur in the vadose zone, understanding
unsaturated flow and transport in such settings requires knowledge
of their hydraulic properties. Some gravel deposits occur in heavily
contaminated vadose zones such as the Hanford Site in Washington
State, where radioactive wastes have leaked. Gravels are also an
important component in engineered capillary barriers for subsurface
waste isolation. However, relatively little information is available
on the unsaturated hydraulic properties of gravels. In a recent
study (Tokunaga et al., 2002), the levels of residual saturation
in Hanford gravels were found to be high, in the range of 0.1 to
0.2. The present work addresses a much broader range of matric (capillary)
potentials and saturations in Hanford gravels, and includes characterization
of intragranular porosity and water film thicknesses on external
grain surfaces.
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 Moisture retention in 2 and 6 mm. Hanford gravels, over a wide range of matric (water) potentials. Measurement methods used are indicated along the x-axis as (a) vapor-pressure regulation, (b) pressure plate, and (c) suction plate. The vapor-pressure equilibration region data were obtained in adsorption mode. The suction plate and pressure plate data were obtained in drainage mode.
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