Geocentrifuge Research Laboratory
Analysis of Capillary Diversion Length in Landfill Covers Using a Geocentrifuge
Earl D. Mattson and Hideo Nakajima, INL - Angelos N. Findikakis and Julio Garcia, Bechtel National, Inc.
Geocentrifuge Research Facility
Capillary barriers are often constructed on a sloped landfill in an effort to promote surface drainage of precipitation events. The sloped capillary barrier also promotes lateral subsurface drainage at the capillary interface. Experiments are being conducted to examining the predictive models of this phenomenon using the geocentrifuge. Two-dimensional scaled models of capillary barriers are being spun at a variety of slopes, g-forces, and with varying textural contrasts. Results of these experiments are captured in-flight through the use of video cameras and multiple soil physics monitoring equipment. The result of our geocentrifuge efforts are a wide variety of experimental simulations that are difficult to obtain in traditional laboratory and field testing and data to compare to existing theoretical results.
Dye streamlines as captured by the video camera during the geocentrifuge experiement.
Coupled Flow and Reactivity in Variably Saturated Porous Media
Carl D. Palmer, and Earl D. Mattson, INL - Robert W. Smith, University of Idaho
Improved models of contaminant migration in heterogeneous, variably saturated, porous media are required to better define the long-term stewardship requirements for U.S. Department of Energy (DOE) lands and to assist in the design of effective vadose-zone barriers to contaminant migrations. The objective of our three-year project is to meet the DOE need by developing new experimental approaches to describe adsorption and transport of contaminants in heterogeneous, variably saturated media (i.e., the vadose zone). The research specifically addresses the behavior of strontium, a high priority DOE contaminant. However, the key benefit of this research is improved conceptual models of how all contaminants migrate through heterogeneous, variably saturated, porous media. Research activities are driven by the hypothesis that the reactivity of variably saturated, porous media is dependent on the moisture content of the medium and can be represented by a relatively simple function applicable over a range of scales, contaminants, and media. A key and novel aspect of our research is the use of the 2-meter radius geocentrifuge capabilities at INL to conduct unsaturated reactive transport experiments. The experimental approach using the geocentrifuge provides data in a much shorter time period than conventional methods allowing us to complete more experiments and explore a wider range of moisture contents. The vadose zone research being done in this project will demonstrate the utility of environmental geocentrifuge experimental approaches and their applicability to DOE’s vadose zone research needs.
Experimental stochastic analysis of unsaturated flow using a geocentrifuge
Robert Lenhart, Roelof Versteg, Alexandre Tartakovsky, and Hideo Nakajima, INL
Predicting the movement of water through heterogeneous porous media is not well understood, especially at low water contents. To test stochastic and conceptual models of unsaturated water behavior in layered porous media, experimental data using a geocentrifuge is being compared to theory and model predictions. In one set of experiments, the layering sequence of porous media in each experiment will represent a different realization of a random saturated hydraulic conductivity field. Statistics (mean and variance) of the experimental water contents will be used for testing a stochastic model of unsaturated water flow. In another set of experiments, the unsaturated water behavior at fine-over-coarse particle size interfaces is examined. Both water content sensors and a three-dimensional electrical resistance tomography system will be developed for use in a geocentrifuge to measure water flow through porous media. The knowledge obtained from the project will advance the state-of-the-science for understanding water movement through heterogeneous porous media, which is critically important for better predicting the migration and fate of contaminants and radionuclides through the subsurface.
Colloid Migration in Saturated and Unsaturated Media: Influence of Surface Chemistry and Accelerated Testing Using a Geocentrifuge
George Redden, INL , - Patricia J. Culligan, Columbia University
Accelerated transport of actinide contaminants in the subsurface is thought to be facilitated, in part, by association with colloids or pseudocolloids. This project, in collaboration with the Massachusetts Institute of Technology, uses a geocentrifuge to conduct accelerated colloid transport studies in order to determine which principles govern migration of colloidal particles in porous media. In the geocentrifuge experiments, transport of model colloids will be measured in a porous media system that replicates soil moisture conditions in the field. The experimental technique uses a two-dimensional "transparent soil" profile made of crushed, pre-wetted Pyrex glass. Below the model water table, the material is saturated with an optical fluid of matching refractive and dispersive indices. Colloid movement is monitored using fluorescent tags and particle tracking software. These experiments will be performed initially on MIT's 1-m geocentrifuge. This work will provide fundamental insight into how colloids move in porous media and what surface chemical parameters affect migration. It will also serve as one of a number of basis studies at INL directed toward the engineered movement and targeting of synthetic colloids in subsurface environments.