Undrained factor of safety

[LiLZhiMiNG]

foundation of a building on a clay layer 50m deep, Cu=87kPa
unit weight 20KN/m^3 are to be bored piles.Density 23KN/m^3 and E=20 000MPa.they are 1m in diameter and embedded to a depth of 16m. Each pile subjected to vertical load of 1000KN.
With that info
I have worked out ultimate undrained shaft resistance of a single pile and ultimate undrained base resistance of a single pile. With these 2 results, how do I go about finding the overall undrained factor of safety?

 

[BigH]

Divide the "undrained capacity" by the applied load. Normally, one determines the undrained capacity and applies a factor of safety to determine the allowable load (based on strength). There are various twists and turns on what factor of safety to apply. Some apply to overall capacity - some apply different safety factors to the shaft and the base. See Tomlinson's book on pile design (also in his foundation book).