Отправлено: 18.08.08 05:57. Заголовок: Electrokinetic in rocks: Laboratory measurements in sandstone and volcanic samples

Electrokinetic in rocks: Laboratory measurements in sandstone and volcanic samples
Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, Volume 25, Issue 4, 2000, Pages 329-332
L. Jouniauxa, , , M. L. Bernardb, J. P. Pozzi, a and M. Zamora, b

a Йcole Normale Supйrieure, Dept. T. A. O., 24 Rue Lhomond, 75005, Paris, France b Laboratoire de Gйomatйriaux, Institut de Physique du Globe de Paris, 4 place jussieu, 75005, Paris, France

Received 29 September 1998; accepted 20 October 1999. ; Available online 6 July 2000.




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Abstract
The streaming potential due to fluid flow in rocks was measured on saturated sandstones. During triaxial failure test, the electrokinetic coupling coefficient was increased at about 72–86% of the failure stress. This increase is thought to be due to an increase of the macroscopic zeta potential in the shear zone where new surfaces are created and connected, allowing fluid to flow through these new cracks. The streaming potential variations could therefore be used as a precursor of the rupture. Measurements were also performed on volcanic samples, with the aim of using electrokinetic phenomena to monitor volcanic activity. Streaming potential was found to depend on the transport properties i. e., permeability and formation factor. Theoretical consideration suggest that such a dependence should be caused by surface conductivity, but this is not the case here.