There was a need for foundations in sensitive locations as part of an extensive new development in the Royal Botanic Gardens, Kew. The Children’s Garden construction included the installation of several large timber structures in close proximity to important tree specimens which needed to be protected.
QuadraBuild were approached by the main contractor to provide foundations for the new structures, including a large elevated timber walkway around a protected Oak tree. The nature of the location and sensitivity of the tree meant that excavation for concrete foundations was quickly ruled out as an option. Most piling systems, including traditional screw piles, are likely to cause damage to the tree roots which was unacceptable for this important specimen.
QuadraPile foundations were approved due to the relatively small diameter whilst still obtaining sufficient load capacity for the structure meaning they would have minimal impact on the important tree and would provide suitable foundations for the large elevated walkway.
A combination of 100mm and 64mm diameter piles could be used to suit the load capacity at each position and further minimise any impact on the tree. All the piles provide a permanent foundation but can be removed and recycled at a later date if the need arises.
The lightweight installation equipment, which is all transportable by hand, means no ground-bearing or tracked rig is needed and there’s no requirement for any piling mat or special access arrangements.
A collaborative design approach was taken between the main contractor, structure supplier and QuadraBuild which resulted in the piles being installed in agreed positions with steel brackets to accept the structure. Adequate tolerance was built into the steelwork to enable piles to be relocated slightly to avoid tree roots. A carefully planned installation process then ensured that piles would be positioned to avoid the roots whilst still providing the foundations required for the structure.
Vertical and angled piles were used in conjunction to take the imposed compression and tension loads as well as horizontal forces from wind and people using the structure.
In situ proof testing provided confirmation that the piles will support the required loads.
The timber superstructure could then be assembled onto the steelwork and the foundations hidden under a new low-impact surface.
The use of QuadraPile, which is manufactured from an aluminium alloy, removes the chance of contaminating the ground with any other substances such as concrete.
The project was completed in spring 2019 and Kew Children’s Garden has now opened to the public after receiving extensive press coverage.