Design drilled shafts for overhead cantilever sign structures

[courtpara]

I am involved in drilled shaft design where the shaft will resist both torsion and axial load in addition to the moment from overhead cantilever sign structure. The shaft will be supported in medium dense silty sand/sandy silt soils. Anyone have any idea how to verify the stability against torsion and axial load?

 

[Ron]

How about a unity check?

 

[PSlem]

I don't have mathcad to try it, but here's a program

http://www.dot.state.fl.us/structures/proglib.shtm