Limit pressure (puD)

[Entey91]

Hi!
I noticed that the maximum soil resistance in soft clay appears to be underestimated in the current model.

Given a soil with the following properties:
-Undrained shear strength (Su) = 30 kPa
-Unit weight = 18 kN/m³
-Strain at 50% (ε₅₀) = 0.015
-J = 0.5

And a pile with a pipe section:
-Diameter = 0.812 m
-Wall thickness = 0.025 m

According to API RP 2GEO, the maximum p–y resistance for clay should be:
-For deep clay: 9 × Su × D = 9 × 30 × 0.812 = 219.24 kN/m
-For shallow clay at the surface (z = 0): 3 × Su × D = 73.08 kN/m

However, in the model results I obtain:
-At depth: 157.52 kN/m instead of 219.24
-At surface (z = 0): 52.51 kN/m instead of 73.08

Could you please explain the reason for this discrepancy? Is there any correction factor or implementation detail that affects the limiting pressure?

[TchilDill]

Hi @Entey91,

The reason is cause you are using "cyclic" curves.

If you were to use static curves you would get the results you are looking for.