Experimental assessment and sequential flow–deformation analysis of dewatering strategies in sheet pile-supported excavations

This study evaluates wellpoint and drain dewatering systems through laboratory experiments and sequentially coupled flow–deformation numerical modeling at full-scale geometry (× 20). A 1/20-scale physical model with sixteen pumping wells and six observation wells monitored groundwater drawdown around a 30 × 30 cm 2 excavation. The internal deep drain (h1) achieved the greatest groundwater reduction and highest vertical base settlement (ratio U v max / U h max = 2.48; 81.8% increase relative to the dry reference), whereas the wellpoint system minimized lateral wall displacement while maintaining moderate uplift ( U v max / U h max = 2.55; 24.6% rate of change), providing balanced internal stress reduction with lower shear and bending forces. Construction sequencing significantly influenced excavation response: pre-dewatering (“dewatering then excavation”) reduced excavation uplift by up to − 283.5% compared with the dry reference, while the global factor of safety remained nearly insensitive (< 0.86% variation). These results indicate that combining the wellpoint system with optimized execution sequencing offers the most effective strategy to control groundwater, limit lateral wall movements, and reduce basal heave in excavations in loose to medium-dense sandy soils.