L-PILE Input Question, Service or Factored to determine embedment

[LittleGator]

The minimum drilled shaft embedment length we use 1.33 times is the length at which additional embedment does not result in a reduced deflection at the pile head (TxDOT Guide).

Since lateral deflection is a service limit state, should we use service loads when we run LPILE to develop the deflection versus embedment table? Is the factor of safety the 33% increase in shaft length? Or, does the Geotechnical Engineer include the factor of safety in the soil properties they provide? Or, should load factored (strength) inputs be used?

 

[STVU]

If all you are after is the lateral load capacity of drilled shafts, "Soil Engineering, Testing & Remediation" by F.H. Chen has it covered in chapter 8. He doesn't mention it, but the charts are based on a maximum of 1/2" deflection.

If, however, you want to produce a chart, Budhu & Davies have a very good method. A small software performs this calculation. That software comes with "Foundations & Earth Structures" 2007 book by Muni Budhu.

Budhu and Davies assume that the pile is fully supportd along its length, which is closer to reality. LPILE uses the spring analogy. Somehow, I find LPILE to have complicated input.

 

[TexCE2009]

If you are determining the length of the pile, you need to used the service loads. Generally the Geotech has already provided the safety factors in the allowable values you use. If you are doing the structural design of the pile, then use the Load Factors (strength design).