Modified expression of Kozeny–Carman equation based on semilog–sigmoid function

Abstract

A modified Kozeny–Carman (KC) equation is presented based on a semilog–sigmoid (SS) function of a soil’s particle size distribution (PSD). The KC equation is widely used to estimate soil permeability. However, a more effective use of the equation requires the accurate measurement of the specific surface area of the soil per unit volume. In this study, it is demonstrated that the specific surface area can be derived from the SS function, which simply but accurately represents the soil’s PSD. The modified KC equation is also extended in terms of uniformity and sorting coefficients for its potential use in geotechnical applications. The applicability of the modified KC equation is confirmed through a comparison of the theoretical results of over 50 permeability tests that yielded values ranging from 1 × 10−5 to 1 × 10−1 m/s.