Netherhampton Road, Salisbury

Initially, the project had been specified to use a granular piling mat with a traditional pile and ground beam solution. However, SPEEDECK proposed an alternative solution with a vastly reduced dig quantities; this meant that less waste needed removal from sites, which in turn lessened the environmental impact caused by waste transport and processing. This revised approach resulted in several advantages:

Simplified Excavation: The need for extensive excavation for the ground beam solution was eliminated.

Reduced Preparatory Work: The concrete blinding solution significantly reduced the preparatory work and muck away associated with a traditional granular piling mat approach.

Minimised Site Storage: The piled raft solution negated the need for site storage for bulk materials used with the precast ground beam method.

Cost Savings: A 37% cost saving was achieved with the non-voided piled raft solution.

The ground conditions at Netherhampton Road, consisting of River Terrace Deposits over Seaford Chalk Formation, required careful consideration in geotechnical planning and design. Key geotechnical considerations included:

-Ground Stability:  Ensuring stability and load-bearing capacity to counter the weak, structure-less chalk.

-Reduced Excavation: The reduced level dig allowed us to minimise excavation work within the Chalk formations, designing a foundation suitable for these ground conditions. Removing the need for a piling mat meant large cost savings were made for the client.

– Heave – SPEEDECK Prepared a heave report for the warranty providers approval which mitigated the requirement for underslab void formers, further saving the amount of dig out required for the site.

– Dissolution Feature Risk – Due to the weak structureless nature of this chalk, a risk assessment was prepared to ensure that the future dwellings were not at risk from complications as a result of dissolution. A detailed pile design was developed in order to negate this risk.

The construction phase of the Netherhampton Road project was meticulously planned to maximise efficiency and minimise disruptions. The 27-week construction programme was divided into three visits, each lasting nine weeks. This schedule included allowances for the completion of under-slab drainage and services between piling and slab works. Key construction highlights included:

– Exclusion Zones: Addressing the presence of power cables near specific plots, including a 3m exclusion zone and installing shrouded cables and goalposts at 3.5m for safety.

-Rapid Foundation Installation: Utilisation of the piled raft system enabled quicker and more cost-effective foundation installation than traditional methods.