Sheet Pile Deflection

[rubsy]

Hi everybody! I need your help. We have an on-going project, Cistern tank. We used sheet piles with horizontal struts. When the struts were removed the sheet pile deflected at about 12 inches. The excavation depth is 6.50 meters. How can you compute the allowable deflection for sheet pile?

 

[GeoPaveTraffic]

Why were the struts removed?

As for the allowable deflection; there are two things to be checked. One is the structural capacity of the sheet pile in bending. Simply calculate the bending moment, convert that the the stress in the outer fibers and compare to the allowable stress for the steel.

The second is the effect of the deflection on what you are trying to protect. It does not matter if the steel is ok if the building/utility/etc. that you are protecting falls apart.

If you give us some additional information, we may be able to help.

 

[DRC1]

When were the struts removed? Typically the struts are removed during the backfill operation with the fill at about the same level they were installed. If they are removed with out sufficent fill in place, large deflections are possible. There are no published limits specific to sheet piles, but at 12 inches, I woud check the stresss levels. It is hard to restore the sheets once they have moved. If the movement can be tolerated, a light frame at the top can help control any increases in stress.