Secant Piles and FEM

[InDepth]

When modeling a secant pile wall in FEM,
1) What is the assumption of wall friction between the secant piles and the soil? Is there a way to place an element modelling the interface that has a maximum based on the maximum friction the soil can develop?

2) Do you normally model the primary and secondary secant pile? or can you assume a stiffness per foot of length. I have a case where the primary piles on extend 2'-0" below excavation while the secondary reinforced piles extend 20'-0" below excavation. Is there any issue with modelling the secant pile wall as continous to 20'-0" rather than modelling discrete? any impact on settlment and movement results?

 

[DRC1]

That depend somwhat on the size of the piles and soil conditions. Generally the secondary piles act as soldier piles and the primary piles as the lagging. General US practice for soldier piles is to treat them as dicrete units, However, there are european practices
I have read that analyze as a continuos wall, with additional embedment for the toe.