Following a detailed geotechnical review, SPEEDECK proposed a mixed solution of CFA (continuous flight auger) and pre-cast driven piles supporting a reinforced concrete raft. Driven piles were adopted to non-heave plots, limiting the extent of contaminated soil removal, while CFA piles were required in heave plots to achieve the necessary tension anchorage. This combined approach streamlined delivery, reduced client risk, and avoided unnecessary excavation of contaminated soils.
Concept Design
Design Engineering
The raft design utilised a 300mm thick reinforced concrete slab, selected to minimise pile numbers and reduce the need for excavation of deeper contaminated material. 160mm RDS voidformers were specified beneath plots within tree influence to mitigate heave risk. Piles were designed in accordance with Eurocode standards, achieving a maximum safe working load of 310kN. Pile lengths ranged from 8.0m to 10.0m.
The scheme delivered a total raft slab area of 2,458m². Integration of piling and slab into a single substructure package provided a technically robust, warranty-compliant solution that safeguarded long-term performance.
Construction
SPEEDECK delivered all piling, raft construction, and underslab services within an 11-week programme. This included pile installation, voidformer placement, raft construction, reinforcement, and integration of underslab drainage. By combining these elements into one package, client management time was significantly reduced and follow-on trades benefited from a predictable, clean, and safe working platform.
