Numerical analysis of unsteady flow through unsaturated soil of uniform sized spheres with distinct packing arrangements

Flow of water through an unsaturated soil having four stable packing arrangements is studied numerically. The soil consists of near uniformly sized sand particles having cubic, orthorhombic, tetragonal-sphenoidal and rhombohedral packings. The soil parameters are obtained by Rawls and Brakensiek Regression equations and van-Genuchten model. A mathematical model is developed using the Darcy's law, van-Genuchten equations and mass balance of the fluid phase. The model is discretized by using an implicit finite difference technique imposed with the boundary conditions of step change in the inflow pressure of soil initially maintained at a uniform suction pressure. The cubic packing has the highest water content and Darcy's velocity, the rhombohedral packing has the highest relative hydraulic conductivity but the effective hydraulic conductivity is the highest for the cubic packing. The close packed structure in the rhombohedral packing results into lesser fall in relative and effective hydraulic conductivities with head whereas it is large in the cubic packing. The mathematical model is equally valid for the soil consisting of sorted particles. Copyright (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The flow of water through unsaturated soil with four stable packing arrangements was numerically studied. The study found that the different packing arrangements resulted in variations in water content, hydraulic conductivity, and effective hydraulic conductivity.