| Autor: |
Jackson, P.D., Northmore, K.J., Entwisle, D.C., Gunn, D.A., Milodowski, A.E., Boardman, D.I., Zourmpakis, A., Rogers, C.D.F., Jefferson, I., Dixon, N. |
| Zdroj: |
The Quarterly Journal of Engineering Geology and Hydrogeology; May 2006, Vol. 39 Issue: 2 p151-172, 22p |
| Abstrakt: |
Amodel of electrical conduction through clay-coated, silt-sized quartz-grains inter-connected by clay-bridges (e.g. brickearth) is developed. Underpinned by SEM studies of brickearth, the model predicts resistivity to be proportional to the size of the quartz-grains, where the resistance afforded by clay grain-coatings and clay-bridges is comparable. The model accommodates resistivity that increases through bridge breakage and decreases through bridge compression. The resistivity of in-situ undisturbed brickearth was found to be in the range 15 to 35 ohm-m. At such low values we demonstrate that electrical flow is dominated by conduction within clay-coatings and their interconnecting clay-bridges, rather than in mobile pore-water. A small electrode array, buried at shallow depth beneath the load plate (1.0 m by 1.0 m) of a field collapse experiment, monitored resistivity to a depth of 1.5 m over a 260 hour period. While the water level beneath the load plate remained below 1.0 m depth, the resulting 3D inverted resistivity models detected water injected immediately beneath the plate; recording rapid increases, in stages over 90 minutes, in the depth interval 0.45 to 0.75 m directly under the plate, during what appears to be collapse. These increases are attributed to breaking of clay-bridges weakened by injected water. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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