Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9537934 | Engineering Geology | 2005 | 8 Pages |
Abstract
The diffusivity anisotropy of ions through rock pore water was evaluated quantitatively by through-diffusion experiments on a rhyolite rock having anisotropic pore structure. The rhyolite has planar flow structure with elongated pore shapes to the flow direction (X-Y plane). Diffusion coefficients of K+ ions for the direction perpendicular to this flow structure (Z-direction) were about 5-9 times smaller than those for the orthogonal parallel directions (X- and Y-direction). Pore geometrical analyses on backscattered electron microscopic images indicated that the pore length ratios among the X-, Y-, and Z-direction were roughly 2Â :Â 2Â :Â 1. This shorter pore length for the Z-direction appears to reduce pore connectivity, causing larger tortuosity and smaller diffusivity for this direction. This diffusivity anisotropy needs to be taken into account for precise modeling of diffusion-limited geological processes such as contaminant transport and rock deformation.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geotechnical Engineering and Engineering Geology
Authors
Tadashi Yokoyama, Satoru Nakashima,