Continuum percolation theory for water retention and hydraulic conductivity of fractal soils: estimation of the critical volume fraction for percolation

摘要

Systematic experimental deviations from theoretical predictions for water retention characteristics of fractal porous media develop at a moisture content, θ_d. Below θ_d larger suction pressures are required than would otherwise be predicted from the implied fractal pore-size distribution. Inferred values of θ_d were shown to be compatible with observed values of the volumetric moisture content, θ_t, at which solute diffusion vanishes. The comparison was based on an accurate phenomenological result for θ_t. The approximate equivalence of the two moisture contents was interpreted in the context of continuum percolation theory (at low moisture contents, below a critical volume fraction of water, α_c, connections for capillary flow are interrupted, leading to a near vanishing of solute diffusion and increasing enormously the time required for equilibration to new pressures). The experimental results for θ_d are now investigated to determine whether their values are generally compatible with theoretically based estimates for α_c.