Two-Tiered Sheet Pile Wall Systems: Design, Execution, and Field Performance-PPT Presentation

PPT Presentation

Pdf Summary

The presentation reviews the benefits, challenges, and design lessons of two-tier sheet pile retaining walls, using two pedestrian bridge projects in Western Australia.<br /><br />Two-tier systems can provide improved stability and load distribution, suit constrained sites, reduce the need for heavy sheet piles or additional bracing, and lower concrete use and environmental impacts. Their performance depends, however, on the interaction between tiers, ground conditions, construction sequencing, and nearby infrastructure.<br /><br />At Malaga Pedestrian Bridge, a temporary two-tier wall was selected to avoid underground services and fit within project boundaries. Unexpectedly high groundwater, vibration during sheet installation, and construction effects contributed to substantial upper-wall movement and displacement of a nearby noise wall. A PLAXIS soil–structure interaction model was calibrated against monitoring data and used to assess remedial measures. These included installing steel sections to stiffen the lower tier, straightening and propping the noise wall, jet grouting around its footings, and leaving sheet piles in place to avoid vibration from extraction. No further excessive movement was observed after remedial work.<br /><br />At Belmont Pedestrian Bridge, both wall tiers deflected more than expected before major equipment loading. Contributing factors included increased fill between tiers, reduced spacing, roller compaction near the wall, and over-excavation. Responses included limiting platform height, using steel mats beneath rigs and cranes, controlling equipment stand-off distances, and restricting excavation during operations. Monitoring and comparison with model predictions helped estimate further movement and guide construction decisions.<br /><br />Key lessons are to model interaction between tiers and account for surcharge, groundwater, vibration, and nearby structures; control installation geometry and construction sequence; involve temporary-works designers early; and establish staged monitoring with clear response procedures.

Keywords

two-tier sheet pile walls

retaining walls

pedestrian bridge

Western Australia

soil-structure interaction

groundwater

construction monitoring

sheet pile installation

temporary works

PLAXIS model