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Sheet Pile Design in Peat Soil 1

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VVang

Civil/Environmental
Jan 30, 2024
6
I am trying to design and size sheet piles for driving into basically peat soil. The sheet piles will be permanent and their only role is to prevent bank erosion around a pump Since peat is unstable, tie-downs would be useless. The intention is to drive piles down to stable foundation and have the sheet piles supported by the piles. I have never designed sheet piles before, how would I determine what sheet pile size is required? I plan to treat have the sheet piles carry the load to the piles but is there a way to choose which sheet pile dimension and thickness will work?

My intention is to design the sheet pile as a cantilever retaining wall (I would ignore any passive pressure since it wont be much at all for peat soil), determine the load applied by the peat soil and use that to size the sheet pile thickness. I would then use that load to also determine how far spaced I need my piles. Is this a viable path to determine what I need?
 
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I have never designed sheet piles before...

Start by reading and understanding as much you can from one of the (free) sheet piling handbooks , such as "ArcelorMittal Piling Handbook". More practical info than a textbook.

Don't try to learn it all, begin with the basics. Then you will may be able to return here to ask specific questions. Doubtful that an online forum will be able to teach you how to start from scratch and design steel sheet piling... although if anyone can it will be PEinc.

 
Helpful as always, SRE...

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-Dik
 
what do you mean exactly when you say 'sheet piles supported by the piles'?

can you share a cross section. If you are worried about bank erosion, why not look at using some armor stone/rip rap?

 
You are on the right track, but as SlideRuleEra mentioned, a guide would be helpful. Many are available online, but I would start with your soil mechanics textbook from college, if you have one. It should have a section on design of cantilever sheet pile walls. If you do not have a textbook, then the guide mentioned by SlideRuleEra, or the guide from US Steel, or guides from the US Army Corps of Engineers, are all available free online.

As a starting point, the embedment of the sheet pile will be about twice the length of the portion which extends above grade. With peat, it might be even longer. Peat will have a small phi value, which means it will have a higher active pressure and a lower passive resistance.

DaveAtkins
 
Check for design of cantilevered and anchored, non-gravity walls in manuals from CALTRANS, AASHTO, and FHWA. They should all have much info on designing SSP walls. Also, check Chapter 7, Earth-Retaining Structures, in Robert Ratay's 2012 3rd edition of Temporary Structures in Construction. Your bigger problem could be choosing the proper design properties for the peat.

 
Sorry gents I think the biggest issue with this proposal is that the OP is planning on driving piles and then driving sheet piles to rest on the piles. Construction with that type of accuracy is impossible. For starters, how do you cut off the pile when you reach your depth, so that the pile will allow the sheet pile to rest on its head.

I am shocked none of you have commented on this, or am I missing the obvious??
 
The obvious is that VVang said, "I have never designed sheet piles before, how would I determine what sheet pile size is required?" At this time, I believe that VVang's scheme of supporting the sheets on top of driven piles is unclear without a sketch and is secondary to VVang's learning how to design traditional sheet pile walls. VVang needs to learn basics before trying to design something that sounds very sketchy and possibly undoable.

 
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