Calculation model and experimental study on permeability coefficient of coarse-grained soil

The permeability coefficient is the key parameter to demonstrate the permeability of soil, and its calculation model with a high preciseness is hard to be determined. Based on Poiseuille¢s Law, the soil in laminar flow is assumed as fine tubular clusters and a permeation physical model is then established. According to the meso-mechanism of water head loss, an overlapping coefficient is introduced, and a theoretical formula for calculating permeability coefficient is derived with specific physical meaning based on Darcy's Law, where porosity and equivalent particle size both function as basic parameters. Permeability tests of six groups of coarse-grained soils with single particle size are carried out. The overlapping coefficient is fitted according to the experimental data, and the formula for calculating the overlapping coefficient is then obtained. It is found that the calculated results obtained from the permeability coefficient formula are almost in accordance with the experimental ones. In order to verify the applicability of the permeability coefficient formula, the experimental data of sandy soil and mixed coarse-grained soil in relevant literatures are calculated by the formula proposed in the study, and the results are in accordance with the measured values. It is also found that the accuracy of the formula in this paper is much higher than those in existing literatures with a high accuracy and reasonability when considering a comparatively large size range of particles(Mixed coarse-grained soil with particle size less than 20 mm and sandy soil with particle size ranging from 0.1 to 5 mm are considered). Finally, the applicability of the formula is analyzed and summarized. © 2019, Science Press. All right reserved.