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Cantilevered permanent sheet pile bulkhead

Cantilevered permanent sheet pile bulkhead

Cantilevered permanent sheet pile bulkhead

Good morning all! I have been lurking for a while and have rec'd plenty of support over the years. Here is my situation. I have an existing tied back timber bulkhead that is to remain, however, the owner wants to gain some space and construct a new sheet pile bulkhead on the water side of the existing timber system. My first thought is to install cantilevered steel sheet pile on 3 sides....sort of like a 3 sided cofferdam, but to be a permanent structure. The goal is to back fill between the timber system and the new steel system. I was looking at the thread here: thread255-444737: Three sided excavtion - again but my example would not have a whaler on it if done according to current plan.

Based on some quick calcs, deflection would be 5.50 inches at the top of the sheet. Side elevation and plan attached.
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RE: Cantilevered permanent sheet pile bulkhead

whats the question here?

We can comment on suitability etc but need more information (soil type, retained height etc) and a more specific question?

RE: Cantilevered permanent sheet pile bulkhead

Thanks! Retained height above the dredge line is 14 ft. Soil is a 110 pcf granular material on the land side for the first 8 ft. of depth. after that it is a 105 pcf clay material down to 100+ ft. My question is: what are your thoughts on just cantilevering it? Intuitively I want to put a whaler and a corner angle strut, but in the case of a cantilever I really should not need it. I'm just curious as to some best practices, recommendations and curious as to if this has been done before. Thanks

RE: Cantilevered permanent sheet pile bulkhead

5.5 inches of deflection is too much. Either your soils are bad, your sheet pile section is too small, or you are using too many or too high of safety factors. A 14' high waterfront bulkhead is pretty high for a cantilevered wall with lagged, hydrostatic pressure, especially if the bulkhead needs to resist any surcharge loads or mooring forces. If you do not want to use tieback anchors or tie rods with deadmen, you may need a larger sheet pile section or possibly a combi-wall.


RE: Cantilevered permanent sheet pile bulkhead

We usually limit our deflection to 2", maybe 3" in some situations, for cantilevered bulkheads with no structures within the influence of the wall. See if you can increase the sheet size to get deflection down.

RE: Cantilevered permanent sheet pile bulkhead

Consider adding some sacrificial thickness to accommodate corrosion. With your height you will be deflection controlled, I have used 2% of the exposed height with a max or 3 inches and 15 ft max exposed height for cantilever sheet piles. Above 12 ft you probably should start thinking combi wall.

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