Liquefaction Analysis for a Pier 2

[MTNClimber]

When looking at liquefaction potential for a marine structure, such as a pier, it's common to have a relatively large head of seawater above the mudline. This can drive the effective stress down to a negative value causing a medium dense or dense sand layer to be potentially liquefiable using the methods by Idriss and Boulanger.

I was wondering how you typically handle this situation. Do you actually consider this to be true or is there something else that should be taken in account?

 

[r13]

If you know the solution of founding structures on land with soil having liquefaction potential, then more or less is applicable to the marine structures. The first question will be that, is there alternative method of support instead of founding in the problematic soil. Another question will be, is there a suitable founding method, such as box vs solid pile, to lessen the impact. I don't quite follow the claim - "negative effective stress", as the soil stress can be completely lost, then the net stress remains is the water pressure. Am I wrong?

 

[EireChch]

How can the height of the water column above ground surface (or seabed) cause negative effective stress?

Effective stress is not affected by the depth of water?

 

[MTNClimber]

Thanks EireChch - You're right. There's an issue with the excel file that was developed. Effective stress cannot become negative. Not sure why I didn't think about that more before I posted.

 

[EireChch]

Brain fart - get them all the time