Permeability of saturated sands, soils and clays

Abstract

It is shown that the permeability of a water-saturated sand or fine powder can be calculated with considerable accuracy, if the porosity and the specific surface are known. In particular, the Kozeny theory here discussed leads to a very useful relationship between permeability and porosity. It is shown that clays do not conform to the theory in its simple form, but that it may be modified to give a satisfactory representation of the data available. The physical grounds for this modified theory are discussed in some detail, and it is shown that, while it is open to criticism, it is at least in harmony with our present knowledge of clays.An important deduction which follows from the modified theory is that clays may have zero permeability at quite considerable porosities, e.g. at ∈ = 0·207 for a clay soil, and ∈ = 0·355 for a plastic clay.