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One of the concepts students in geotechnical engineering courses seem to have the most trouble with is estimating stresses in concrete piles during pick-up and setting them in place to drive.  The basic problem is that it’s sometimes hard to get our heads around the analytical simplification of the actual situation.  Let’s start by looking at the operation itself.  These first photos come from a job in Delaware in 1998, using a Vulcan 530 to drive cylinder piles.

The pile starts on the ground. What we have here is “one-point pickup” where only one line is used to pick up the pile. It’s put in a certain place (more about that later) in this case using a “choker.” (Some piles have pickup lifting eyes, they are best cast into the pile at the time of manufacture.) In this position the pile is horizontal. Once the crane operator lifts the choker…