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Hollow pile patent promises greener, reusable building foundations

A tubular concrete pile developed and patented at City University London and tested by Balfour Beatty could result in greener building foundations that can be reused in the future.
by Luke Nava

Concrete piles commonly form the foundations of tall buildings in city centre developments where the ground is soft. They are constructed by drilling a hole - often 30m deep and 1-2m in diameter - and filling it with reinforced concrete.

The technique has been used since the 1960s, yet the lifespan of many commercial buildings is only 25-30 years. This has resulted in the ground in urban areas being filled with concrete piles, which cannot be reused when redevelopment takes place because their condition and structural integrity is unknown or they are simply in the wrong place

The new design - known as SuRe Pile - promises to address this by creating a hollow cavity at the centre of the pile. This has numerous benefits: the amount of concrete used and hence the environmental impact of the building is reduced; the cavity could be used for green building services, such as rainwater storage or ground source heat pumps; and the foundations are future proofed. For example, when a site is redeveloped in several decades' time, the cavity will enable the inspection and testing of the pile to its bottom, while a smaller pile could be constructed in a new location within the hole.

The idea was developed by Dr Andrew McNamara, a Senior Lecturer in Civil Engineering, and colleagues at City. He says: "The legacy of concrete piles in densely packed cities such as London is becoming a real problem - it can take two days and £30,000 to remove an old pile on a redevelopment site. Our aim is to ensure that future generations don't have to face this issue, by enabling the construction industry to build more adaptable foundations today."

The SuRe Pile concept has already been tested by Balfour Beatty Ground Engineering at a Wembley construction site. It was built alongside a full-size solid pile of the same depth and outer diameter and both were loaded to 1000 tonnes - an industry-standard test. The SuRe Pile was found to be as strong and stable as the traditional design.

Tony Suckling, Technical Director at Balfour Beatty Ground Engineering, says: "The reduced volume of concrete used in the SuRe Pile, as well the flexibility of the concept will make it incredibly useful in creating greener buildings in future and ensuring new developments meet environmental accreditation schemes such as BREEAM and LEED."

City University London is now seeking more industrial partners - including piling contractors, consulting engineers, architects and property developers - to take the idea forward, through further testing and commercial deployment.

It is hosting a launch evening for SuRe Pile on Wednesday 30 November 2011. Interested parties can register their attendance with Nadia Zernina-Forde, City's Research and Enterprise Marketing and Business Development Manager, at Nadia.Zernina-Forde.1@city.ac.uk.

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City, University of London is an independent member institution of the University of London. Established by Royal Charter in 1836, the University of London consists of 18 independent member institutions with outstanding global reputations and several prestigious central academic bodies and activities.