Electrical‐hydraulic relationships observed for unconsolidated sediments

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 ( S por ), 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 S por is nonlinear and appears to depend upon material type. Further examination shows that σ″ is well correlated with effective grain size ( d 10 ) 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.