I would not use the terms CFA and driving in the same description. It is one or the other. Nor would I use the term average ground conditions.
For Auger Cast-in-Place Continuous Flight Auger in medium clay (say, Nspt = 10) down to 20m, expect about 10 minutes going down and 15 minutes going up.
Depends not just on soil but also your equipment (drill head torque and concrete pump).
If you are trying to establish any form of agreement based on this estimate, beware. I once spent three days in arbitration once when a contractor sued for more money after he used an estimate of his to calculate how long it would take to do the job. Unfortunately for him he was allowed to do a test installation before the job was bid and it's result was twice as long as his estimate for his bid. The job was auger cast piles extended to solid rock.
When I was supervising CFA piles in the late 80s it was dependent on just in time, good quality concrete supply. Also out of sequence working to avoid damage to newly constructed piles from boring adjacent at 3 x pile diameter.
Back then 10 piles a day would be poor bonus for the crew, 20 piles a day good going.
Many thanks for your reply gentlemen. Really helpful. Of course, I shouldn't use CFA and driving in the same description, that was a daft way to put it.
