Continuous flight auger (CFA) or driven piling is traditionally used for low rise structures in the UK. CFA piling generates arisings (or spoil), which require muck-away from site and current design methods can result in reasonably long piles for relatively light loads. In some instances, a precast driven piled solution can provide a solution to these issues. However there are sites across the UK where it is not possible/preferred to utilise driven piles, and an augered solution is required. Roger Bullivant Ltd currently provides a viable alternative for higher loaded situations (the continuous helical displacement or CHD pile). However these can often be too large for lightly loaded structures such as housing, schools, and commercial or industrial structures. In response to this, Roger Bullivant Ltd has developed an innovative displacement solution in a smaller 300mm diameter pile – the continuous displacement auger (or CDA pile).
This technique has the benefits expected of a CFA or bored pile in terms of low vibrations and low noise (compared to driven techniques) and provides additional benefits! So, what are the advantages of CDA?
- CDA is ideal for light to moderately loaded piles, typically up to 500kN compression loading across the residential, public, commercial, and industrial sectors. CDA piles have been installed to date for low rise housing schemes, schools, and industrial buildings.
- The pile is suitable for a range of soils including soft to stiff clays, silts, loose granular soils, and weaker chalk.
- Due to the smaller diameter, the CDA pile uses less concrete per linear metre of pile to construct (compared to our higher capacity CHD pile).
- CDA piles can also be designed to cater for the same heave forces, shear, and tension forces as an equivalent diameter CFA pile.
Roger Bullivant recently did a project at the Ramsden Hall Academy in Billericay, Essex, where the CDA pile design provided the same capacity as the 300mm CFA piles, despite being 40% shorter. This saved not only cost in relation to materials used, but vastly reduced the amount of muckaway required from site. In addition, our bespoke rigs are easily converted on site between CFA, CHD, and CDA piles, for example if locally non-displacement piles are required due to sensitive nearby structures.
With quality paramount, all boring and concreting are computer-controlled and recorded using onboard instrumentation to ensure high-quality piles are constructed. This also allows remote monitoring and data capture.
This article was paid for by Roger Bullivant
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