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Walls for Excavation

Walls for Excavation

(OP)
Good day everyone!

We will be rehabilitating an interchange, which includes widening and bridge and roads.
We have a problem wherein the sloping sides of the embankment of an existing elevated bridge approach will be excavated because a road will be constructed beside it (see attached file, the red will the finished grade)
The height of the excavation will be approximately 8 to 10 meters. The existing bridge approach is assumed (most likely) to be from fill materials.

We have researched some methods for retaining it, well, first that came to our mind is sheet pile. But we think that it might be impossible since we cannot anchor it.
We think that we can use bore-pile walls for it. Will it be the best option? If yes, can you give us good reference on the design and construction methodology?

Thanks in advanced!

Very Truly Yours,

- andru18

RE: Walls for Excavation

Solider pile walls with wood lagging being slid in from the top down sounds like a viable option. Though with the retained heights you state, the soldier piles would more than likely have to be anchored. Possibly you could use a really big W-section and not have to anchor them.

RE: Walls for Excavation

Drilled piers is probably the only option to get a strong enough section to cantilever up 10 meters. They will go pretty deep also depending on foundation conditions. TXDOT probably does as much of this as anyone. Look up their design guides.

RE: Walls for Excavation

We often design sheeting jobs like you have described. We have used both SSP and SB's with lagging. For your wall height (8 to 10 m), the wall should be tied back. Why do you say that you cannot use tiebacks? Is there any bedrock at or just below proposed excavation subgrade? Cantilevering soldier beams 8 to 10 meters high at close horizontal spacing may not be economical compared to installing smaller soldier beams at greater horizontal spacing and with tieback anchors. The attached photo shows a tied back sheeting wall in Stage 2, after the same wall was used to build Stage 1. Stage 1 used angled, grouted, tieback anchors. Stage 2 used horizontal tie rods with deadmen buried in the Stage 1 backfill.

www.PeirceEngineering.com

RE: Walls for Excavation

Have you considered jacking/boring the tiebacks? Then you could use a soldier pile wall with any lagging you choose. My choice would be H-pile or wide flanges with hollow core concrete slab lagging fitted between the flanges.

RE: Walls for Excavation

(OP)
Thanks everyone!

I have read all your comments, upon discussing this with proper authorities, we opted to use secant pile walls instead. We think it is the best choice.

Do you have links for the typical plans of secant pile walls? Or what should be included in the plans (general notes, typical details, construction sequence)
I already have some of those, just for comparison.

Very Truly Yours,

- andru18

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