Validation of Whole-Core Determination of Soil Hydraulic Properties
EMSL Project ID
25668
Abstract
The EMSL Subsurface Flow and Transport Laboratory developed a fully automated Hydraulic Property Apparatus (HPA) that is a significant advance in measurement technology. The HPA uses the multistep outflow method, in which increasing pressure increments are used to drain the sample and the resulting outflow time series is used with an inverse technique to estimate parameters that can be used to describe hydraulic properties. Adequately characterizing the hydraulic properties of porous media is necessary to make accurate predictions of contaminant fate and transport. The HPA method overcomes many of the limitations of previous methods, including long test durations, non-reproducibility of subsampling, differences between lab-packed cores and field cores, and operator bias. The one thing the HPA method lacks is a direct measurement of conductivity (in association with water content and pressure measurements) to validate the technique. That limitation can be overcome by adding the capability to conduct the controlled flux method in sequence with the multistep outflow method. The controlled flux method works as its name implies, namely, applying a known flux and monitoring the soil core till water contents and pressures reach equilibrium. Adding such a capability will give the HPA the ability to evaluate methodologies and provide a firm foundation of experimental data that confirms its applicability to soils at DOE sites.
This proposal seeks to determine what combination of dynamic and static measurements and analyses is sufficient to accurately characterize the hydraulic properties of porous media. The overall approach is to design, build, and successfully test an instrument and controlling software to measure the complete suite of soil hydraulic properties with minimal sample disturbance or operator bias. To that end,
the HPA (and associated software controls) will be modified to interface with one or more precision micropumps. The modified HPA will be used to conduct a multistep outflow test on a core. Following that test, the modified HPA will be used to conduct a controlled flux test on the same core. Thus, all measurements of pressure, water content, and outflow will made be on the same sample with no disturbance between tests. The multistep outflow test will be analyzed using the inverse technique described by Hopmans et al. (2002). The result will be compared with the measurements from the controlled flux test. In addition, the controlled flux test results will be analyzed using an inverse technique and the parameter results compared with the parameters derived from inversion of the multistep outflow test. The one critical milestone of this proposal is successfully demonstrating that a precision micropump can be integrated with the HPA. This proposal will generate unique datasets that will confirm the validity of the measurement and estimation techniques. The results will be submitted to a journal.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2008-06-01
End Date
2009-06-07
Status
Closed
Released Data Link
Team
Principal Investigator