Moisture characteristics of Hanford gravels: Bulk, grain-surface, and intragranular components Page: 8 of 18
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
grain is only about 10-3 g g-i (from Eq.[l]). The third feature shown in these results is that
surface film moisture characteristics do not exhibit hysteresis. This lack of hysteresis in film
characteristics was demonstrated previously on a fractured rock surface (Tokunaga and Wan,
1997).
Qualitative aspects of film flow along external surfaces of Hanford gravel can be deduced
from measurements just described. Film transmissivity, the unit gradient flux per surface length
transverse to the flow direction, depends on surface topography and matric potential (Tokunaga
and Wan, 1997). Since the vesicular pits are sparsely distributed rather than interconnected (Figs.
6 and 7), these deep surface features do not contribute significantly to film flow. Recall that the
grain surfaces have been smoothed by glacial and fluvial weathering, resulting in rmsr values in
the range of 1 pm. Under finite matric potentials, such smooth surfaces cannot support thick
(e.g., > 2 pm) water films. Therefore, fast, unsaturated flow is not possible in these gravels
below the matric potential at which pendular rings are no longer interconnected, since water
films then control flow (Wan and Tokunaga, 1997).
CONCLUSIONS
Various techniques were used to quantify moisture characteristics of the 2 and 6 mm
fractions of Hanford gravels. Differences between moisture characteristics for these two grain-
size fractions were only important in the near-zero matric potential region associated with
drainage of the primary pore network. Over a broad range of matric potentials, water content
remains practically unchanged, and nearly identical for the two grain-sizes. Water retention in
this range is associated with intragranular pores, and amounts to about 10% of the total porosity.
The specific surface area of these gravels is fairly high (about 11 m2 g"), and largely associated
with the intragranular domain. The combination of large grain-size, significant intragranular
porosity, and significant intragranular surface area make these gravels sinks and sources for
solutes, with potentially long, diffusion-limited equilibration times. External grain surfaces have
rmsr of about 1 pm over most locations, with isolated deep pits. Such surface topography does
not support thick water films at matric potentials less than about -1 kPa, and therefore will not
support fast film flow at lower energies. Although measurements were done on specific size
fractions of Hanford gravels, the conclusions concerning the intragranular domain and grain-
surface characteristics remain valid for these gravels in well-graded mixtures of grain-size.
ACKNOWLEDGMENTS
We thank Andrew Mei, Eduardo Saiz, and Robert Conners of LBNL, and Tony Lanzirotti
(University of Chicago) for technical support, and John Zachara, Robert Lenhard, Steve Smith,
and Bruce Bjornstad of PNNL for samples of Hanford formation sediment. We also thank Sam
Ricci, Jr., and Ricci Brothers Sand Company, Port Norris, NJ for providing quartz gravel
samples. Helpful internal review comments by Tim Kneafsey (LBNL) are gratefully
acknowledged. This work was carried out under U.S. Dept. of Energy (DOE) Contract No. DE-
AC03-76SF00098, with funding provided by the DOE, Environmental Management Science
Program. Research carried out (in part) at the National Synchrotron Light Source, Brookhaven
National Laboratory, which is supported by the U.S. Department of Energy, Division of
Materials Sciences and Division of Chemical Sciences under contract number DE-AC02-
98CH10886.page 8.
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Tokunaga, Tetsu K.; Olson, Keith R. & Wan, Jiamin. Moisture characteristics of Hanford gravels: Bulk, grain-surface, and intragranular components, article, May 2, 2003; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc737752/m1/8/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.