Problem

When putting finishing touches to the £582m Birmingham New Hospitals Project at the University Hospital Trust’s site at the end of last year, a new bridge was required to provide a sheltered link to existing buildings. Investigations discovered up to 10m of very soft cohesive deposits, so WYG, Balfour Beatty’s Consulting Engineers for the project, approached PowerPile with a view to using the UPP400 PowerPile system to provide additional support to the existing foundations.

“The main issue for us was the location of the work, at the main entrance to the existing hospital, within the corridor that forms the main hospital street. Disruption and vibration were key considerations for the design, so rather than a traditional piled solution, we thought of PowerPile.” said Andy Garland, Associate at WYG.

Solution

PowerPile teams completed the installation in three shifts working at night, to minimise disruption.

Prior to the work, a trial PowerPile was tested on site. PowerPile represents a new era in polymer injection technology, allowing for precise prediction of outcomes. “The results of the trial compared favourably with those anticipated from the analysis, with settlement values slightly less than predicted and an ultimate bearing capacity greater than predicted from a conventional analysis using standard piling theory,” says Stephen Cooper, Geotechnical Manager.

“The additional conservatism in PowerPile design was due to the improvement of surrounding soils during the insitu expansion of the PowerPile.”

Following the completion of the trial to the satisfaction of the engineers, the installation of 10 PowerPiles was undertaken and the bridge unit successfully installed.