Relating Hydraulic Conductivity to Particle Size Using DEM

Abstract

For over 100 years it has been accepted that the permeability or hydraulic conductivity of a soil is controlled by the size of pores through which the fluid flows, and that this pore size should be a function of particle sizes. All well-known formulas (such as the empirical Hazen or analytical Kozeny-Carman) are based on the squared value of some characteristic particle or pore size. Recent work has established which particles control the porosity or density of a granular material, so it follows that these particles may also govern the hydraulic conductivity. In this work, a new yet simple technique was used to obtain a characteristic "smallest" particle size, which is a function of both the particle size distribution and the geometrical packing. The use of this new proposed characteristic particle size was shown to be valid both theoretically and in comparison with the characteristic particle or pore sizes used in classical predictive methods for the permeability of granular materials. A very simple fractal theory showed what the characteristic particle size that controls conductivity should be, and a simple discrete element simulation was used to confirm the result.