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

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The paper examines the design, construction, and field performance of two-tiered temporary cantilevered sheet pile walls used for bridge works in Perth, Australia. These systems can support excavations up to about 6 m in constrained urban locations where conventional anchored walls may conflict with services or project boundaries.<br /><br />At the Malaga Pedestrian Bridge, excavation and groundwater conditions led to unexpectedly large movements in the upper-tier wall and an adjacent noise wall. The design had not adequately accounted for interaction between the tiers, construction vibrations, noise-wall loading, or dewatering effects. PLAXIS modelling showed that lower-tier movements could substantially increase upper-tier deflections. The response included strengthening both tiers with steel UC sections, revising the excavation sequence, monitoring movements, and stabilising and realigning the noise wall.<br /><br />At the Belmont Pedestrian Bridge, changes to excavation levels, fill, compaction, equipment loads, and tier spacing caused deflections to exceed initial predictions. Updated numerical analyses were calibrated against monitoring data and used to guide construction restrictions and estimate movements from subsequent work. The analysis indicated that increasing tier separation reduced deflections most effectively up to roughly 3.5 m; about 4.5 m was considered a practical, cost-effective spacing.<br /><br />The case studies show that two-tier walls require explicit assessment of soil–structure interaction, cumulative tier deflections, load paths, groundwater control, and effects on nearby infrastructure. Reliable performance also depends on suitable numerical modelling, coordinated design, careful installation and excavation sequencing, control of heavy equipment and vibration, and ongoing monitoring. Early collaboration between geotechnical and structural designers can help manage risks and improve temporary-works solutions.

Keywords

temporary cantilevered sheet pile walls

two-tiered sheet pile walls

bridge excavation

geotechnical design

field performance

soil-structure interaction

PLAXIS modelling

groundwater control

construction monitoring

Perth Australia