LPILE Soil Parameters Question - cohension/undrained shear strength

[cad0211]

I am trying to work my way through using LPILE for the first time and I'm trying to replicate references from previous jobs from before I was here.

For the soil parameters, are cohesion and undrained shear strength considered the same thing? I'm seeing them used almost interchangeably and they have the same units.

 

[MTNClimber]

Cohesion typically is 1/2 the undrained shear strength. Please keep all of your LPile questions under one thread.

See below.

 

[geomane]

Cohesion and undrained shear strength can be considered the same thing, under certain loading conditions. If you run an unconsolidated-undrained triaxial test, the undrained shear strength that results from this test can be input as a cohesion.

MTNClimber, cohesion is typically half of unconfined compressive strength.

 

[MTNClimber]

You’re right. I mixed the words in my head last night.

 

[RGKVI]

Undrained (total stress) for clay soils in the short term (temporary works) which generally use Cu (kPa) and phi = zero. Use drained for granular soils short term and long term.

Drained (effective stress) for long term clayey soils where Cohesion is usually zero (kPa) and phi is the drained angle of shear resistance say 25 degrees.