Kensington Row, London

Richard Ball

Richard Ball

Technical Director

Tel: 01483 310600 Email Richard

Joseph Slattery

Associate

Tel: +353 (0)1 554 6210

Email Joseph

Client

Walsh Associates

Services

  • Ground movement analysis
  • Temporary works design and design checking
  • Monitoring strategy and contingency planning

CGL takes innovative approach in design of temporary propping systems

CGL’s innovative approach to ground engineering paid off successfully in an unconventional temporary propping system for a deep basement excavation.

Working alongside the client, principal contractor and the project’s structural engineers, CGL played a key role in the analysis and design of a buttress pile temporary propping system for a deep basement in Kensington. Active Network Rail tracks are within 5m of the site boundary so it was critical that risks of movement would be effectively controlled by the temporary works solution.

On the site, a buttress pile system supported a secant pile wall within a 10m deep excavation. The buttress piles acted with the secant pile wall, through a rigid connection in the form of a capping beam between both elements. This increased the rotational and lateral stiffness of the wall and ensured overall stability and serviceability is maintained. This approach required the use of finite difference analysis software, FLAC, to model the complex soil structure interaction.

As a value engineered solution, the buttress pile system superseded the original conventional proposal of constructing a temporary earth berm and installing a large network of steel propping and thrust blocks. This revolutionary approach has proven to be a cost effective and practical solution in comparison to conventional propping systems. Additionally, the buttress pile solution has allowed for an accelerated construction programme by eliminating restricted working spaces within the excavation.

During the excavation and basement construction the site team confirmed that the wall performed well with monitored movements falling within allowable and predicted limits. These suggest the buttress pile temporary support system performed very effectively and is a great example of what value engineering can achieve.