Wet‐End Deviations from Scaling of the Water Retention Characteristics of Fractal Porous Media

Abstract

A previous work investigated the dry‐end deviation from fractal scaling of water retention characteristics of a suite of 43 U.S. Department of Energy (USDOE) Hanford site soils in relationship with the vanishing of solute diffusion at a moisture content θt It was found that the deviation from fractal scaling of the water retention set on at a moisture content typically about 0.06 higher than the moisture content at which solute diffusion vanishes. Assuming that the vanishing of solute diffusion resulted from a lack of continuity of the water phase, we interpreted the deviation from fractal scaling in terms of a lack of water‐phase continuity rather than as a breakdown of the fractal model. Now the wet‐end deviations from fractal scaling of the same suite of soils are investigated. It is shown that the wet‐end moisture contents at which the deviation occurs are correlated with the critical volume fraction for percolation and with the dry‐end deviations. However, wet‐end deviations occur at moisture contents closer to full saturation than do dry‐end deviations from zero saturation. This contrast between the wet and dry ends of the water retention curve, h(θ), is suggested to be a result of the role of equilibration in the experimental determination of h(θ), and thus to be traceable to the much lower values of the hydraulic conductivity, K, at the dry end.