Holdfast Training Services Trial Blog

I’ve cut the notes off this version to allow it all to go on one page. There is a jetty around three sides of the cofferdam at this point but omitted for clarity. Stage 2 is actually a tie to stop the cofferdam collapsing outwards when a piling rig is put on top of it. The cofferdam should be water tight at this point and so water can be pumped out and the tie (I’ve put forward the idea of it be capable of being both tie and strut depending on construction stage) installed from the jetty, yes you will probably need a man in a boat or a working platform hung off the sheets perhaps.
Stage 3 – Prop is a tie for Stage 4, which may or may not be needed.
Stage 5 – Again a victim of cropped notes, concrete terminated just above required level, then casing removed, then hole backfilled before excavation.
Stage 10 – Sheets either burnt off by divers, realistic in my mind or extracted as you say BUT the pile cap is cast against the sheets greatly increasing the friction to try and pull it out in my view.

I still think my initial option was practical although I accept that piling from a barge may prove prohibitively expensive, but the sheets can be smaller as you use the water and tides to benefit pumping and equalise pressure.