Factor of Safety Values for Driven Piles

[grabens]

I am looking for opinions on an acceptable factor of safety for driven piles or a reference that addresses this issue.

I have seen a FOS of 2 for skin friction and a FOS of 3 for end bearing. I have seen a straight FOS of 2 to 2.5 on pile capacity (tip + end bearing). Just curious to see what others think or are using.

Thanks in advance

 

[Ron]

Generally use FS=2 for all.

 

[Ron]

Oops. Pushed too fast...

For true end bearing only I would increase the factor of safety, since when this "true" condition is encountered, there is often some associated down drag on the pile as well.

 

[BigH]

Tomlinson covers pile safety factors in his Foundation Design and Construction book. Because of the different ways in which the mobilized skin and base capacities develop for different type of installations - there are "partial safety factors" applied. With the new codes coming out (Eurocode, for example), there seems to be getting to be some complexity - but Tomlinson suggests a FS or 2.5 on Qs+Qb but not more than Qs/1.5 + Qb/3 for piles in cohesionless materials. For piles in cohesive soils, FS Qult/2 or no more than Qs + Qb/3. I suggest that one consults Tomlinson's book first hand to note the various caveats made.