Estimating porosity and particle size for hydraulic conductivity of binary mixed soils containing two different-sized silica particles

This study investigates the hydraulic conductivity (K) of binary mixed soils containing two different-sized silica particles, with the ultimate goal of developing the porosity (n) and equivalent particle size (d_eq) estimating formulas for binary mixed soils. Theoretical backgrounds for K of mixed soils were reviewed. In addition, a series of constant head permeameter tests for mixtures with three different size ratios between small and large particles were performed. It is demonstrated that the K of tested materials decreases with an increase in volume fraction of small particles (SC_V) when SC_V < SC*_V (volumetric critical small particle content) because of the decreases in both n and d_eq. In contrast, when SC_V > SC*_V, K shows less change with SC_V because of the offset mechanism between increased n and decreased d_eq. Additionally, n and d_eq estimating methods for mixed soils are suggested in this study and compared with the experimental results.