Above – LIDAR (Light Detection and Ranging) used without man-entry to point cloud a vault-type structure

As one of the UK’s leading specialist geotechnical and geoenvironmental consultancies, we are in a unique position to bring together experience with resources and capabilities such as applying advanced PLAXIS 3D finite element analysis to a range of ground related problems. Using a combination of detailed analysis and careful planning CGL can often improve plans by developing lean solutions to difficult ground issues that reduce costs or timescales.

Project examples:

Basement excavation in chalk – the original project proposal for the Subsea 7 headquarters included a contiguous pile wall solution to prevent ground movement beneath a Network Rail line beside this double-basement development in chalk. Our detailed analysis showed a cost saving combination of open cut excavation and king posts with robust monitoring controls could be used with observational methods to manage risk. The project won an award from Ground Engineering in 2016.

Buttress piles in temporary works – CGL developed a solution that enabled cost effective and programme reducing construction of a double basement at Prince of Wales Drive, Battersea. CGL designed buttress piles to support a retaining wall for a double level basement excavation next to sensitive infrastructure including a gas pressure reduction system which is situated above a future London Underground line. The piles extend 10.5m above the formation level and have already generated significant interest within the construction community.

Reuse of foundations – our detailed investigations determined the condition of the existing concrete piles beneath offices at Lambeth High Street. The building was planned for redevelopment into an 11 storey residential building with a piled raft which would require additional 20m piles to support the load.

Using the information we gained with historical construction records, we demonstrated the viability of piled raft designs for the new building. Our modelling using PLAXIS 3D software showed no new piles would be required and critically our conclusions were accepted by NHBC.

Overall, our analysis has considerably reduced foundation and basement costs, shortened the construction programme and minimised use of new materials for the project.

Safe investigation of subterranean vaults – we recently completed pre-demolition ground investigations at the famous New Scotland Yard building in central London which is to be redeveloped. Historical maps showed that vaults were once constructed beneath the road in front of the building with no record of their final condition. Opening the vaults from above in order to investigate them had safety risks so we developed a “keyhole” technique of drilling into the side of the vaults from the basement and inserting a probe capable of scanning the interior for 3D modelling by advanced software. The project was selected as a finalist for the Ground Investigation Project of the Year award by Ground Engineering in 2017.

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