Wave Forces and A Seawall

[DaveVikingPE]

I have an instance where a vertical concrete wall will extend at least six feet above grade (landward side; the mudline on the seward side is about 10 feet below landward grade, thus the wall is about 16 feet high) and will be subject to direct wave impacts. The concrete wall is to be no greater than two feet thick. The return period is a 100-year storm.

The wave force, computed by the Minikin method, has a resultant of 69 kips/ft of wall. The location of the force's resultant is 14 feet above the mudline.

Constraints: the seawall is to be a vertical bulkhead-type wall with minimal excavation allowed; that is, it's not allowed to be a T-wall. NB: scour protection will be incorporated into the design.

Idea: Make it an I-wall.

Questions: OK, so it's an I-wall. What's the required section modulus of my steel that extends into the ground forming the "I"? Etc.

Other info: I am of the mind that the configuration desired is impossible. What do you folks think?

 

[RWF7437]

Is steel sheet piling a possibility you might consider?

Russ Faust
Salem, OR USA

 

[DaveVikingPE]

It's really a trick question... Steel sheet piling is a possibility, but the moment at the embedment point is really high; too high for a traditional I wall - unless an uneconomical embeddment depth is specified. Intuitively, a massive counterfort wall is probably the right way to go... but we're constrained such that a counterfort wall isn't allowed. The story is still unfolding...

 

[RWF7437]

Not sure what "uneconomical embedment" means in this case. If greater embedment is possible and will accomplish your goal isn't that at least one possible solution ? Yes, it may cost more than you would normally expect but does it cost more than other alternatives ?

Russ

 

[DaveVikingPE]

If you have to drive sheet piles to 70 ft and your actual wall is only 15 ft above grade and you have a couple of miles of wall, it's uneconomical.

 

[RWF7437]

Hello Dave,

Maybe the following link will give you some alternatives to consider.

http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-2502/toc.htm

Russ