Soldier Pile Wall - Soil Conditions 1

[civengr]

New here. The soil in the area is a firm clay. For modeling the soldier pile wall below the dredge line, can we assume the soil will be cohesive in the long term or must we model the soil as granular for the long term?
I though only Geotechs can help me with this.

 

[PEinc]

Long term - granular

 

[civengr]

Thank you. Can you tell me why?

 

[civengr]

Sorry, I guess I did not frame it right. I understand that we are designing for the drained condition since over a period of say 200 years, undrained condition may not apply. But is it required to design a structure for that long term? Am I making any sense?

 

[PEinc]

It's pretty common and sometimes specified to design permanent structures for a drained condition where cohesion is assumed to approach zero. It is usually also more conservative to use c = 0 with a relatvely low phi angle. Structures may be termed permanent if they are to remain in service for as little as 1.5 or 2 years.

 

[DRC1]

Although lab testing in clay is always best, typically normally consolidated clays will gain strength with drainge, so the undrained strength will control. Overly consolidated clays generally lose strength with drainage, although that can be a slow process, therefore drained strength will control. Agin this is a generality and should be based on testing or at least some local experience.