The construction of cofferdams poses significant challenges in hydraulic engineering, where optimized design is essential for risk mitigation and construction safety. This study investigates the performance of a Larssen pile-reinforced cofferdam in a field ridge remediation project through integrated numerical modeling and limit equilibrium analysis. A coupled hydro-mechanical model was established, incorporating saturated-unsaturated seepage theory and an elastic-plastic constitutive model to simulate groundwater movement and slope stability. The results demonstrate that the Larssen sheet piles serve as an effective subsurface barrier, significantly impeding both soil and water flow. The implemented seepage cutoff measures induced a substantial hydraulic head difference across the cofferdam, leading to a marked reduction in both hydraulic gradient and water flux. Notably, simulated vertical displacements at pile tops during groundwater drawdown showed strong agreement with field measurements. The magnitude and variation trend of vertical displacements at the pile tops closely match field measurements during groundwater drawdown. Underwater side filling causes minimal pile-top settlement, while top filling results in greater settlement. Additionally, the zone of maximum ground surface settlement migrated from the cofferdam top toward the downstream slope-face. These results suggest that well-engineered Larssen sheet pile reinforcement can effectively control seepage, enhance the slope stability, and improve the structural integrity of earth-rock cofferdams.
Lin et al. (Fri,) studied this question.