Electrical‐hydraulic relationships observed for unconsolidated sediments

Abstract

We use complex conductivity measurements to predict the hydraulic conductivity (K) of unconsolidated materials. The samples include natural sediments and artificial sand/clay mixtures. We apply the Börner et al. [1996] model, which is based on the Kozeny‐Carman equation and incorporates electrical estimates of formation factor (F) and specific surface area per unit volume‐to‐porosity ratio (Spor), from the real (σ′) and imaginary (σ″) conductivity components respectively. We find that K correlates with σ″ but shows no correlation with F, which we attribute to the wide range in grain size for these materials. The Börner model appears primarily dependent on the K ‐ σ″ relation. The relationship between σ″ and Spor is nonlinear and appears to depend upon material type. Further examination shows that σ″ is well correlated with effective grain size (d10) and is relatively independent of the material type. We propose a simple Hazen‐type equation in which the effective grain size is estimated from σ″. This simple model provides order of magnitude estimates of K for a range of unconsolidated sediments.