Risks to ground and rig stability from overflighting on construction of continuous flight auger (CFA) piles are highlighted by a new guidance document published by the Federation of Piling Specialists (FPS).
The FPS has said that overflighting occurs when the auger is over-rotated and excessive soil is removed creating the potential for the ground around the tool to become unstable and result in settlement. According to the FPS, the risks from overflighting can be exacerbated when insufficient concrete is placed to account for the overflighting and the integrity of the pile and its capacity can be affected.
FPS chairman Martin Blower said: “What this document does is raise wider awareness of the potential risks of over-flighting, loss of support and stability of the working platform that may result in a piling rig or attendant crane overturning. More importantly, the document encourages robust risk management and the controls to be implemented to mitigate such risk.
“Safety is fundamentally important and the FPS encourages all those involved in CFA piling to look at the guidance document and circulate it widely to all those actively participating either in the specification or the delivery of CFA piling on sites.”
The guidance sets out details of when the ground conditions might present a greater risk of overflighting and also the pile spacings that could also create a higher potential for problems. The guidance draws together information regarding existing standards that should be adhered to in order to minimise the risk during design and control measure that can be implemented on site to monitor for signs of overflight during the excavation phase.