The development is for the construction of a workshop and associated hard standing for the transport maintenance depot to support Belfast’s new dynamic public transport scheme. Once opened the facility will service and maintain the city’s new fleet of state-of the-art articulated buses. The site was previously of historic industrial use- located on the docks not far from where the Titanic was constructed!
Soils typically comprised of 1.0m – 3.5m of made ground overlying soft clays and loose sands to a depth of to 5.7m – 11.3m where medium dense sands and gravels were encountered.
Bi-Modulus Columns (BMC’s) were identified to provide the ideal value-engineering solution, providing an improved ground bearing capacity with minimal spoil. To prevent surface disturbance (i.e. ‘egg-box deformation’) across the final pavement, the compacted granular BMC head along with an overlying granular load distribution mattress was sufficient to offer a 1.8m of coverage above the concrete element. The alternative would have required the Main Contractor to have carried out a considerable reduced level dig to remove around 1.8m of unsuitable material across the whole of the site- both costly and time consuming.
This solution allowed the client to construct a ground bearing slab above a 500mm distribution mattress of granular material between the heads of the CMCs and the underside of the slab. This saved the construction of a heavily reinforced slab and much time in cropping down precast piles.