Prediction Method for Hydraulic Conductivity considering the Effect of Sizes of Ellipsoid Soil Particles from the Microscopic Perspective

Abstract

In the existing research studies of hydraulic conductivity, most of them assume that soil consists of spheroidal particles and the value of hydraulic conductivity can be designated by the particle size. In the actual soil layers, the shape of soil particles is mostly ellipsoid or rod-like rather than ideal sphere. Therefore, the prediction of soil permeability using current method often deviates from the actual situation and cannot capture the anisotropy nature of soil without consideration of the effect of the axis size of soil particles in two different directions. To solve this problem, a new theoretical model with three different soil particle arrangements is introduced to derive a new hydraulic conductivity-particle size relationship considering the size difference in two directions. This model, from a microscopic perspective, divides pores into numerous pore units and obtains hydraulic conductivity of each tube unit, eventually predicting the permeability of soil layer based on an equivalence principle. The proposed equation is validated in comparison with experimental data from the existing literature and is proved to have a satisfied accuracy to predict hydraulic conductivity for a wide range of soils, from bentonite-silt mixed soils to sandy soils. The proposed model provides a new perspective for accurately predicting the hydraulic conductivity.

Verification of determination of hydraulic conductivity for coarse soils by empirical formulas based on the density index

“…Generally, lower permeability coefficients were obtained in soils characterized by a higher density index. It should be noted that the value of the permeability coefficient is influenced by the shape of soil particles and their mutual arrangement (Parylak et al, 2013;Zięba, 2016;Shen, Zhu & Gu, 2019;Wrzesiński, 2020). This effect can be ignored in this study, since all sands had the same origin -they are alluvial soils.…”

Suitability of Engineering-Geological Environment on the Basis of Its Permeability Coefficient: Four Case Studies of Fine-Grained Soils

“…Empirical formulae, which are widely used, are based mainly on the grain-size of soils and thus their use, although easy and quick, is subject to significant errors. Often these formulae, based only on grain-size diameters, do not take into account the relationship between porosity, compaction, specific surface area and permeability coefficient [17][18][19][20][21][22].…”