Transient loads and Group effects

[harpoon]

The structural engineer wants to know how much impact group effects have on pile capacity (downward, uplift and lateral) and how much can the loads be increased for transient loads. Does anyone know a good reference for these?

 

[civilperson]

Group effects for driven piles in sand are greater than unity (110% - 145%), and this increase is almost never used in design. Das has formula for piles in clay soils on page 503 of "Principles of Foundation Engineering".