St Johns - Coventry - Secant Bored Pile Wall

Posted by: jamesbinns on Dec. 1, 2008

Secant Bored Pile Wall - St John's, Coventry

Following a successful tender design by Byland, Expanded Piling Limited employed Byland to undertake the detailed contract design of a secant bored pile wall for a large basement as part of a commercial development on St John’s Street, Coventry, adjacent to the ring road.

The bored pile wall was some 275m in linear length with a retained height of 7 to 10m. The wall was designed as a temporary cantilever with local areas of temporary single level propping adjacent to lift pits. Three reinforced concrete basement floor slabs provide permanent propping. Compressional loads of up to 5,000kN per pile were also required in localised areas.

The ground conditions at the site comprise up to 3m of made ground overlying approximately 3m of stiff red clay, with weak becoming strong sandstone bedrock at approximately 5 to 6m depth. Groundwater at the site was recorded at varying levels, the design considered a temporary design water table and a worst case long term design water table based on the possibility of a rising water table in the Coventry district.

Design analysis of the bored pile wall was undertaken using the WALLAP computer program to compute pile lengths for acceptable factors of safety and also to determine the structural bending moments and shear forces.

The 880mm male and female piles were successfully installed by a cased CFA piling system (CSP) method using a Bauer BG36 piling rig.

Byland was also later commissioned to undertake the design of in-situ concrete anchor head blocks for installation of temporary ground anchors where single level temporary propping is required and piles for tower crane foundations.

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