Numerical Analysis of Groundwater Seepage and Exit Gradients in Hydraulic Structures

Abstract

General Background: Seepage beneath hydraulic structure foundations poses significant risks of piping failure and structural instability. Specific Background: Installing vertical sheet piles alters flow paths and mitigates subsurface water pressure under variable upstream heads. Knowledge Gap: Precise comparative quantifications of seepage flow rates and exit gradients with and without sheet piles remain insufficiently detailed for varying head conditions. Aims: This study evaluates seepage discharge and exit gradients under hydraulic heads up to 10 meters using 2D finite element modeling. Results: Omitting sheet piles increases maximum seepage rates from 361.1x10-3 to 491.3x10-3 m3/sec/m and exit gradients from 0.41 to 1.21. Novelty: Quantitative modeling demonstrates that removing sheet piles elevates seepage discharge by 26.5% and exit gradient by 66.6%. Implications: Incorporating sheet piles is essential in foundation design to prevent subsurface erosion and ensure long-term structural safety. Keywords: Exit Gradient, Hydraulic Structures, SEEP/W, Seepage Analysis, Sheet Piles Key Findings Highlights Sheet pile installation decreases peak under-foundation seepage discharge by 26.5 percent at maximum head. Critical exit gradients rise by 66.6 percent when structural cutoff barriers are omitted. Steady-state finite element simulations confirm severe piping risks without foundation sheet piles.