Anchored sheet pile wall design anchor location

[4Boomers]

Is there a rule of thumb, or an easy way to find, the proper location (% of exposed or total wall height) of a singe row of anchor tie-backs for a anchored sheet pile wall?

Any thoughts/suggestions would be appreciated.

Thank you.

 

[BridgeSmith]

I suppose if you're looking for the optimal location, you would have to find the point on a fixed - pinned beam with an overhang, where the positive moment in the span matches the negative moment on the overhang, under the applied loading, which would then be measured from the point of fixity of the sheet piles. It could be derived (and probably has been somewhere), but it would change depending on the balance between the linearly increasing loads (soil pressure) and uniform loads (surcharge).

Most people would assume a simple span from the bottom of the exposed height to an assumed tieback height, calculate the moment on the simple span, calculate the moment on the cantilever portion above the tieback, and maybe go through a couple iterations to get them to approximately balance. That's what I would do, assuming that practical considerations (ease of construction) on the placement of the tieback didn't take precedence over optimizing the sheet piling.

 

[bdbd]

In single anchored retaining systems, I usually like to keep the anchor close to top or at the top to limit the cantilever type deformations, so effect at the ground surface would be minimal. But, this requires more moment capacity. If you are short on moment capacity, get it lower, however, you should check the deformations, especially ground surface settlements. 20% of the exposed length would be a nice start for parametric analyses.

 

[PEinc]

The best location depends on what shape earth pressure distribution you use, what underground structures or utilities you need to avoid, what soil layer you want to anchor into, what soldier beam steel or tieback tendon size you may already have on hand, etc. Are you trying to balance the moment in the soldier beam or limit the tieback DL? These considerations are all part of the design process. However, for many one-tier anchored or braced walls, I first try my brace or tie location down about 0.35 x the exposed wall height when using trapezoidal earth pressure.

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