Composite Cantilever Sheet Piles with Sand Bag Supports 1

[USGeotech]

My client needs to create a temporary sheet pile diversion wall down the middle of river. The sheet pile diversion wall needs to resist about 5 feet of water at normal flow and about 11 feet of water at design flood stage. The sheets will be driven to bedrock to provide a cut-off through the stream bed soil. For most of the wall length, the bedrock is deep enough to get sufficient embedment and allow the sheet piles to cantilever.

At a small section, the bedrock is shallow. When driven to rock, the sheet piles will have enough embedment to resist the normal water level but insufficient embedment to provide adequate cantilever resistance for the design flood. A sketch of the cross-section is attached.

One thought is to place bulk sand bags (3'x3'x3') in front of the sheet piles to provide added support to resist the design flood water level. Is there any reference that provides guidance on designing a sheet pile wall with supplemental support in front similar that provided by the sand bags?

 

[PEinc]

When I have done this, I put extra support (sand bags) on both sides of the sheet piling so that the piling could not fall over into the stream. The sheeting needs to work both ways for all possible loading conditions (water levels). Also, the sand bagged material could be submerged and buoyant (less weight). The soil in the piled sand bags is sloped. Therefore, there would be a significantly reduced coefficient of passive pressure.

http://www.PeirceEngineering.com

 

[USGeotech]

I agree, all of your points are valid and must be considered in the final design. But is there any reference or published method that combines the two dissimilar supports - the passive soil pressure developed on the sheetpiles below the streambed and the lateral capacity of the gravity structure created by the sand bags above the streambed?

 

[PEinc]

I would not design the passive resistance of sand bags any differently than I would for regular streambed soil - except maybe for any sloped surface of the in-place sand bags. I would ignore any effect of the bags and would just consider the soil in the bags.

http://www.PeirceEngineering.com