OWNER:
Hillingdon Council
ENGINEER:
Buro Happold
GENERAL CONTRACTOR:
Buckingham Group Contracting
MAIN FIGURES:
541 Vibro Stone Columns (VSC) installed
Project Details
Following successful collaboration on a previous similar scheme, Buckingham Group approached Menard to find an alternative efficient foundation solution for the development of a new leisure complex to be built for Hillingdon Council, where the base designed called for a piled solution with suspended slab. The new Yiewsley & West Drayton leisure centre will house a 25m swimming pool, training pool, splash-zone, gym and health suite, soft play, climbing wall, youth zone, a café and terrace, and even a rooftop 3G turf football pitch, covering a ground floor area of about 3,400 m².
Ground Conditions
The initial site investigation revealed the presence of a Made Ground layer of variable thickness and stiffness, over clay of the Langley Silt Member and dense gravels of the Lynch Hill Gravel Member, underlain by stiff London Clay. Due to the uncertainty on the characteristics and depth of the Made Ground layer, Menard recommended further ground investigation by Cone Penetration Tests (CPT) to advise on the most appropriate ground improvement solution. This supplementary CPT report confirmed that the Made Ground thickness was varying between 1 m and 4 m deep and was comprising a soft-firm clayey matrix. The Langley Silt Member also appeared soft in some areas.
Solution
In the areas outside of the basement (which was sitting on top of the competent dense sands because of its depth), Menard designed and installed a solution of Vibro Stone Columns (VSC) to avoid piling and allow the use of conventional shallow foundations: pad/strip footings with SLS bearing pressure of 150 kPa and ground bearing slabs with a UDL of up to 75 kPa. This brought significant benefits to the overall project, by reducing the carbon footprint, accelerating and simplifying the construction sequence, and reducing costs.
The VSC have been installed through the made ground and soft clay, at depth between 1 and 4 mbgl. The works have been completed in less than a week on site, ahead of programme.
Sustainable Development
The use of Vibro Stone Columns (VSC) greatly reduced the embodied carbon of the construction, by reducing the quantities of heavy carbon-emitting materials such as concrete (no concrete piles, thinner ground bearing slab) and steel (no pile caps, conventional pad/strip footings). Furthermore, VSC were installed using recycled aggregates instead of quarried stones which lead to a further reduction of the overall carbon footprint of the project.
