Author:
Conca James L.,Wright Judith
Abstract
These studies illustrate the efficacy of a newly developed
unsaturated/saturated flow apparatus (UFA) to decrease significantly the
time required to obtain direct measurements of transport parameters. The UFA
method can be applied to cores of soil, sediment, rock, concrete, or any other
porous media, especially highly unsaturated and relatively impermeable
materials. The UFA method is effective because it allows the operator to set
variables in Darcy"s Law and impose any desired steady-state hydraulic
conductivity. The UFA achieves hydraulic steady-state in hours by using an
adjustable body force (provided by a centrifugal acceleration in the rotating
frame of reference) to drive the fluid, coupled with precision fluid flow
through a rotating seal assembly. The normal operating range of unsaturated
hydraulic conductivity that can be imposed by the UFA is from the saturated
conductivity for that specimen [up to about 10-4
cm/s (10-1 darcy; 10-9
cm2)] down to about 10-11
cm/s (10-8 darcy; 10-16
cm2). For strictly saturated conditions, the UFA can
operate down to 10-14 cm/s. Temperatures can be
adjusted from -20° to 150°C, and constant flow can be imposed during
rotation down to 0·001 mL/h. Several comparisons are made among
K(θ) results, determined on splits of the same
samples using the UFA and other methods, to the van Genuchten/Mualem
estimations derived from water retention data using RETC. A case study is also
discussed involving subsurface hydrostratigraphic mapping and recharge
distribution at a mixed waste site. This study demonstrates the speed,
economy, and direct measurement capability of the UFA that make it optimal for
determining transport behaviour under unsaturated conditions.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
31 articles.
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