Abstract:
This paper presents a comprehensive investigation into the design, construction, and field performance of two-tiered temporary cantilevered sheet pile walls, with a particular focus on their application in deep excavation support within constrained urban environments. As urban infrastructure continues to grow in density and complexity, conventional excavation support systems— such as tiebacks or braced walls— often face limitations due to restricted site access, adjacent structures, and utility conflicts. The two-tiered cantilevered sheet pile wall system offers a practical alternative by allowing for staged excavation and support without the need for extensive lateral bracing or tiebacks, making it particularly suitable for sites with minimal tolerance for construction-related disruptions.
The study centers on two recent infrastructure projects in Perth where this innovative temporary shoring solution was successfully implemented. A detailed comparative analysis is conducted to highlight key engineering considerations, including geotechnical site characterization, soil-structure interaction, wall deflection behavior, and the structural design of each cantilever tier. Emphasis is placed on the stability of the tiered wall system under complex loading conditions, as well as the sequencing of excavation and installation activities to minimize risk and maintain wall performance throughout construction.
Instrumentation and field monitoring were integral to both projects, enabling real-time performance tracking and validation of design assumptions. Ground movements, wall deflections, and pore water pressures were monitored to assess system behavior and its impact on adjacent structures and utilities. The data collected provides insight into the actual performance of the system under varying soil conditions and excavation depths, offering valuable feedback for future design refinements.
The findings from this study underline the importance of optimizing wall geometry, including cantilever heights, sheet pile section selection, and tier spacing, to ensure adequate moment resistance and overall stability. Anchorage methods and installation techniques are also discussed, with recommendations for managing groundwater and minimizing construction-induced settlements.
In conclusion, the paper identifies key lessons learned and best practices that emerged from the case studies. These include strategies for design optimization, construction planning, risk management, and monitoring protocols. The insights gained contribute to a broader understanding of multi-level temporary shoring systems and provide a framework for their successful implementation in similarly constrained urban settings, supporting safer and more efficient construction of underground infrastructure.