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Electrical properties of partially saturated Topopah Spring Tuff: Water distribution as a function of saturation
Author(s) -
Roberts Jeffery J.,
Lin Wunan
Publication year - 1997
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/96wr03905
Subject(s) - saturation (graph theory) , electrical resistivity and conductivity , thermal conduction , materials science , permeability (electromagnetism) , dielectric , relative permeability , water content , mineralogy , soil science , geology , chemistry , geotechnical engineering , porosity , composite material , mathematics , physics , combinatorics , biochemistry , optoelectronics , quantum mechanics , membrane
We have measured the dielectric constant and electrical resistivity of Topopah Spring tuff as a function of saturation at 23° and 40°C. Dry and saturated resistivities can differ by more than 4 orders of magnitude. Frequency‐dependent impedance measurements indicate that the overall electrical response of the rock arises from at least three conduction mechanisms, which we tentatively identify as conduction through adsorbed water on solid surfaces, conduction through isolated pockets of water, and conduction through continuous (bulk) water. The relative contribution of each mechanism varies with saturation. A continuous (bulk) water film is indicated at saturations as low as 35%. Reasonable agreement was found between predicted permeability based on electrical measurements and microstructural parameters using the Kozeny‐Carmen relation and experimentally determined permeabilities. Similarly, good agreement was found between estimates of cation exchange capacity (CEC) based on electrical properties through the Waxman and Smits [1968] equation and published CEC values for tuff.