Double wall sheet pile pier (parallel walls)

[montbIanc]

Hello

Can anyone help with a U.S. design manual for double wall sheet pile piers? This will have water on both sides, not a dry work area on one side. Loads will be gravity, waves, boats and seismic. I've designed sheet pile walls before but am sure that double wall structures have internal stability requirements like circular cofferdams but probably reduced strength because they don't have the nice, circular shape. Aside from strength calculations, guidance on seismic loads is my main concern. I can do the wave and vessel loading.

Thanks in advance for the help.

 

[montbIanc]

I'll give this a bump before trying the retaining walls forum.

 

[TLHS]

Can you give more information? What is this doing if it's two walls but no elevation difference in the water?

 

[montbIanc]

Hi TLHS, it's the wall of a harbor basin - waves outside, boats/small ships on the sheltered inside, vehicles and cranes on top. I might not have explained well the first time. The two sheet pile walls run parallel about 30 feet apart (TBC). They are tied together near the top with anchor rods and infilled with granular fill. Link to example photo below but it will be L-shaped.

https://www.steelpilinggroup.org/wp.../12/brighton-marina-double-wall-cofferdam.jpg

 

[jayrod12]

I would design it for the case where there is no water on the outside, but full of gravel and equipment on the inside. Maybe that's over conservative, but that's just my first gut reaction.

There's also likely tidal/wave action trying to laterally move the entire block of sheet piles and soil one way or the other. In that instance, I would likely design that both sheet piles are working to resist the load from one side. But I'm not sure how to address the fact that there will still be water on the other side, potentially helping resist the wave action.

Hopefully someone who's done a few of these is able to comment. I've only done cofferdams for bridge pier construction, where my only concern is water load.

 

[TLHS]

Dig through the stuff on vulcanhammer and the pile buck manual. That guy is the king of marine piling stuff. I'm seeing a lot of information on cellular construction, like cassions and dolphins and things that's likely transferrable. I'm not immediately seeing double wall construction for jetties, even though it's pretty common. I'd also look at the US Military guides for sheet piles and similar construction. They're very practical.

I've done it, but only in shallow water and in areas where there's basically no external lateral loads, so most of the complications didn't exist and I basically just got to pound the things into the ground, dump infill in between and then do some cross-ties above the water line. Basically, easy mode.

 

[montbIanc]

Thank you, both. TLHS, I'll have a deeper dig through Vulcan Hammer - some of their documents came up by web search (like the circular cofferdam manual) but I didn't find anything for this type of structure. I have turned up some European guidance but it's a bit light on seismic. I also don't want someone showing up later in the project who does know of a US manual and wants to switch.

My main concerns are the internal stability/strength (not sure how to describe) - basically relying on the granular fill to resist the rectangular cross-section shearing into a parallelogram. And whether this resistance is reduced during earthquakes. For the actual seismic load, I will use gravity wall guidance if nothing better found, since it's supposed to act that way (if it doesn't shear internally).

Jayrod - I think it would be too conservative to assume no stabilizing water pressure. The only time the water would be completely absent would be a few minutes before a tsunami wipes it out anyway. The wave load calculations generally calculate a net pressure, so the benefit of the water inside the harbor is included by default.