Secant Pile Walls - Soft and Hard Pile Embedment Depth

[gonutsdonuts]

Hello,

I'm looking to potentially design a secant pile wall for a project we're working on. For a typical secant pile wall there are "soft piles" and "hard piles" - where the soft piles are constructed first and the hard (or reinforced) piles are drilled right through them. I was wondering why the "soft piles" are sometimes detailed to the full depth of the "hard pile" and sometimes not? Is it a construction issue? From a design point of view, it would seem like having the soft piles cut off just below the finished grade elevation would be the best option if wall deflection isn't an issue, as that would work more like a soldier-pile wall. The necessary pile embedment depth is much less for a wall with discrete vertical elements than that same wall with continuous vertical elements...

Thank you!

 

[Retrograde]

You would take the soft piles down if you need to cut off water flow through the section of wall below the bulk excavation level.