Holdfast Training Services Trial Blog

Debond, Debond, Debond!

An interesting loop hole/oversight, that we have come across on site. The main bars for the pile cage are de-bonded using foam down to cut off level.

The designer will never approve foam all the way down to cut off level in case of any drop in the reinforcing cages. (They allow 50-100mm). The piling subcontractor have a tolerance of cage level of -50mm and +150mm in accordance with the ICE Specification for Piling (SPERW). In this case, we have both extremes of +100mm and +150mm, which has resulted in 250mm of bonded concrete.

Normally, this would be easy using a pile cropper or diamond drilling company but not when it is bonded. Back to pneumatic picks by hand.

The drawings and tolerances were all checked by the piling subcontractor, principal contractor, designer and client’s representative. All failed to spot the issue, myself included. I would expect the piling subcontractor to be fully aware of the issue but again nothing was mentioned.

Contractually, nothing that we can do. The pilers are within these individual tolerances. Unfortunately, it falls on the next subcontractor to work through the issue. This means a lot of time and especially Hand Arm Vibration (HAV) as they work around the main bars.

The lesson here is even though the tolerances may appear acceptable in isolation. The sum of these tolerances have resulted in extra time, cost, and H&S risk.