Sheet Piling (single line) to retain water only 2

[shorebob]

I cannot find a combined active and passive pressure diagram for a single line of sheet piling driven into a river mudline to retain one-side hydrostatic load, only, above that mudline. They all show retained earth (shoreline bulkhead), even USS Manual and NAVDOCKS. Thanks for any direction. Bob

 

[Focht3]

As I understand your problem, you plan to install a sheet pile wall in a river. It sounds like a cofferdam; the mudline will be the same on both sides of the sheet pile wall, but the water level will be drawn down on one side.

The effective stress soil parameters are calculated based on the piezometric level at a given point. The differential water pressure is also calculated using the piezometric levels. If the sheets are driven a "sufficient" penetration into a low permeability clay, you can probably ignore the pressure changes due to seepage around the bottom of the sheet piling. In this case, the piezometric level is dependent on the depth below the phreatic surface. The key to this approach is the determination of what constitutes sufficient penetration...

When you assume no underseepage, the net pressure diagram due to water is zero at the top of the upper water level and linearly increases until you reach the lower water table. The water pressure is uniform below this depth, but it isn't zero. The water loads constitute the loads on the bulkhead; the soils exert active and passive pressures on the embedded portion of the sheet piling and offer resistance to the water loads. But they don't contribute to the loads on the sheet piling.

If the sheets are driven into sands, gravels, silts, etc. - or a depth into clay that would permit seepage beneath the bottom of the sheeting, then you will need to do a seepage analysis. The results of the seepage analysis will provide you with the piezometric pressures along both sides of the sheet pile.

I generally recommend that engineers "new" to these kinds of analyses perform a seepage analysis regardless of the problem geometry. And don't forget to check the stability of the "dry" side of the sheet pile wall due to the uplift forces from seepage pressures...



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[GeoPaveTraffic]

You don't state what the purpose of the sheet piles is, however, if it is to prevent water from entering the "dry" side of the sheet piles - you have a problem. I designed a temporary single sheet pile wall back in the early 90's to allow construction of a riverside gambling boat.

Single line sheet pile walls leak like the devil. This is true both above and below the mud line. Leakage above the mud line can be reduced by dumping cinders and sawdust on the river side of the wall, however, significant leakage should still be expected. Also, every time a construction activity vibrated the sheets, more cinders/sawdust was required. This is also true every time the water level changed more than 4 or 5 feet.

If you really need a dry place, design and install a real cofferdam.

 

[DRC1]

Single sheet pile dams are common and can be made to work. Focht3 gives a good outline of the difference between dams in water and dams in earth. The only difference I would point out is that fot the stability and structural design of typical dams (retained heights of about 15 feet)in granular soils, I usually assume a hydrostatic pressure below the dredge line to be the full NET hydrostatic pressure at the dredge line and straight line to zero at the tip. A full seepage anlysis will yield a more accurate result. Also a full seepage anlysis is nessesary if you need a pumping estimate.
GeoPave Traffic points out that the interlocked steel sheetpiles leak. They do. The leakage can be reduced by proper instalation of the sheeting by an experienced marine crew, and using hot rolled sheets such as Bethlehem style(which are now available again) The cold rolled sheets are cheaper to buy but can allow a lot more water. Also it is good to be conservative about the cantileved height of the sheets. Single wall dams do work but require constant pumping and attention. Therefore they are not used as permanent structures, but as temporary structues in which to build permanent structures. If you havee not designed dams in the water before, you should get an engineer who has to check the design.
Good Luck

 

[PSlem]

I did a wall two years ago and got a rubber product from my sheet supplier in bags that we cut into chunks and heated in a pan in a turkey fryer and poured into the interlocks. It did not peel off as adjacent sheets were driven and effectively sealed the joint.