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Estimation of Length-Scales in Soils by MRISoil can be best described as an unconsolidated granular media that forms porous structure. The present macroscopic theory of water transport in porous media rests upon the continuum hypothesis that the physical properties of porous media can be associated with continuous, twice-differentiable field variables whose spatial domain is a set of centroids of Representative Elementary Volume (REV) elements. MRI is an ideal technique to estimate various length-scales in porous media. A 0.267 T permanent magnet at NASA GRC was used for this study. A 2D or 3D spatially-resolved porosity distribution were obtained from the NMR signal strength from each voxel and the spin-lattice relaxation time. A classical spin-warp imaging with Multiple Spin Echos (MSE) was used to evaluate proton density in each voxel. Initial resolution of 256 x 256 was subsequently reduced by averaging neighboring voxels and the porosity convergence was observed. A number of engineered "space candidate" soils such as Isolite(trademark), Zeoponics(trademark), Turface(trademark), and Profile(trademark) were used. Glass beads in the size range between 50 microns to 2 mm were used as well. Initial results with saturated porous samples have shown a good estimate of the average porosity consistent with the gravimetric porosity measurement results. For Profile(trademark) samples with particle sizes ranging between 0.25 to 1 mm and characteristic interparticle pore size of 100 microns the characteristic Darcy scale was estimated to be about delta(sub REV) = 10 mm. Glass beads porosity show clear convergence toward a definite REV which stays constant throughout homogeneous sample. Additional information is included in the original extended abstract.
Document ID
20050203885
Acquisition Source
Glenn Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Daidzic, N. E.
(National Center for Microgravity Research on Fluids and Combustion Cleveland, OH, United States)
Altobelli, S.
(New Mexico Resonance Albuquerque, NM, United States)
Alexander, J. I. D.
(Case Western Reserve Univ. Cleveland, OH, United States)
Date Acquired
September 8, 2013
Publication Date
January 1, 2004
Subject Category
Earth Resources And Remote Sensing
Meeting Information
Meeting: 7th International Conference on Magnetic Resonance in Porous Media (MRPM7)
Location: Palaiseau
Country: France
Start Date: July 4, 2004
End Date: July 8, 2004
Distribution Limits
Public
Copyright
Public Use Permitted.
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