Geophysical Research Letters
Geophysical Research Letters
5 years ago

Physical explanation of Archie's porosity exponent in granular materials: a process-based, pore-scale numerical study

Qifei Niu, Chi Zhang
The empirical Archie's law has been widely used in geosciences and engineering to explain the measured electrical resistivity of many geological materials, but its physical basis has not been fully understood yet. In this study, we use a pore-scale numerical approach combining discrete element-finite different methods to study Archie's porosity exponent m of granular materials over a wide porosity range. Numerical results reveal that at dilute states (e.g., porosity ϕ > ~65%), m is exclusively related to the particle shape and orientation. As the porosity decreases, the electric flow in pore space concentrates progressively near particle contacts and m increases continuously in response to the intensified non-uniformity of the local electrical field. It is also found the increase in m is universally correlated with the volume fraction of pore throats for all the samples regardless of their particle shapes, particle size range, and porosities.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/2017GL076751

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