Numerical Study of Hydraulic Percolation in Porous Media Using Two Hydraulic Structures

Abstract

This article investigates hydraulic percolation in saturated porous media, focusing on containment systems using sheet pile walls and gravity concrete dams. The Laplace equation, which governs hydraulic flow in porous media, is solved using the Finite Element Method through the ANSYS software. The modeling of the porous media employs a planar quadratic element called Plane 55, originally used for thermal problems, composed of four nodes and one hydraulic degree of freedom per node. The numerical results of the water pressure acting on the hydraulic structure, flow rate, and hydraulic gradient at the outlet of the porous media are compared with results obtained in the technical-scientific literature using flow nets. Two different methodologies are used to obtain the rate of seepage: by using the average hydraulic velocity or by calculating the integral of the hydraulic gradient perpendicular to the flow area. Both methodologies are compared and validated in the numerical simulations. The results obtained show a minimum percentage difference of 1.77% and a maximum of 22.72% between the hydraulic flow values obtained by the studied numerical methods when compared to those obtained by the graphical method. This work also demonstrates the importance of mesh refinement for obtaining the flow rate in the studied hydraulic systems. The inadequate refinement of the region around the base of the sheet pile wall can lead to a 149.17% increase in the maximum hydraulic gradient compared to the use of a structured mesh with uniform dimensions, consequently resulting in an overestimated hydraulic flow.

Keywords

• soil hydraulics
• fem
• laplace equation
• steady-state regime