Kimbers Lane Footbridge, A404M
Tel: 01483 310600
- Geotechnical Site Investigation
- Nightshift Highway Works
- Working Platform Design
- Settlement Analysis
- Contractor Support
Geotechnical investigation for bridge replacement
Birse Civils engaged CGL to provide expert geotechnical advice for a bridge replacement scheme on the A404M near Maidenhead, Berkshire.
A Highways Agency survey determined that the Kimbers Lane footbridge, crossing the A404M, did not meet vehicle impact standards and the footbridge should therefore be replaced. To replace the original concrete span bridge and central reservation pier structure, a value engineered solution comprising a metal single span deck was designed. A significant-sized mobile crane was required to remove the existing spans and piers and install the new bridge deck. Although anecdotal evidence suggested problematic ground conditions was in the location, no suitable ground information was available on which to base a working platform design.
In order to determine the underlying strata and provide an appropriate assessment of the suitability of the carriageway as a working platform, it was necessary to undertake a site investigation which involved a cable percussive borehole constructed within the central reservation. Due to the nature of the location and the need for total road closure and, being sensitive to motorists using this passage, the works were undertaken during a weekend nightshift. Various ancillary works, including the removal and reinstatement of the Armco barriers, also took place during this nightshift.
A combination of in-situ testing and laboratory analysis provided appropriate input parameters to allow the working platform design to be completed, and the new bridge to be lifted into place within the programme timing.