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Piling: Why bigger is better

Francis & Lewis International is launching a new large diameter screw pile range.

Francis & Lewis International (FLI) has launched a new range of screw piles. FLI’s research and development team is recognised for innovation and for pushing the boundaries to overcome challenges and create new ideas, solutions and products.

Its latest selection of screw piles is available in tube sizes from 457mm to 610mm, with helices up to 1m in diameter. These new larger products represent a significant increase in the individual pile capacity - more than double - that FLI could previously offer, thus enabling larger structures to be supported with fewer piles.

FLI geotechnical engineer Alex Tollington says: “The ability to offer this significant increase in pile capacity allows FLI to provide competitive solutions in new markets where previously screw piles would not have been considered”

Cohesive soils

The piles can be installed in cohesive soils with a standard penetration test (SPT) value of up to 70 (approximate shear strength of around 300 kPa).

They are installed with FLI’s new PD200 torque motor whose torque has increased the torque that can be applied to piles installation by up to 250%. In a recent trial it took under six minutes to install a 4m deep, 457mm diameter screw pile with a 1m helix.

This is similar time to an equivalent driven pile, but with less noise, vibration and in most cases less plant required for installation.

Alfonso Caso, of FLI’s engineering team, explains: “The increased power of the new torque motor will allow FLI to reduce the time spent on site and therefore limit associated health and safety risks.

“It will also enable FLI to offer a viable option in-ground that was be too hard for screw piles in the past. As well as helping to develop our core markets, the increased capacity of the larger screw piles will support higher loads than were achievable before, opening up new markets, such as buildings or bridges.”

Variable message signs

The large diameter pile range means that FLI can support a variable message sign structure and platform in the highways market on only four large diameter piles, instead of a typical number of eight smaller piles. This means that the frame can be smaller.

The same applies to FLI’s rail division where one pile can be used when traditionally at least three piles would have been utilised.

FLI sales manager Tony Parker adds: “Screw piles should be considered by all foundation designers. They are definitely the way forward, proving quick to install and so increasing productivity and reducing shift/possession time, saving the client time and money.

“Furthermore the installation of screw piles only requires one item of plant which can reduce your carbon footprint. Screw piles also can be easily removed and reused elsewhere, if a site is decommissioned.

‘These piles do not produce the noise and vibration of a driven pile installation so they are environmentally friendly all round. Concrete is often the default solution, and screw piles are only considered when there are access problems or where there is soft ground to depth.”

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