Timber Retaining Wall with Deadman
Timber Retaining Wall with Deadman
(OP)
We have a new project we are considering taking on which is the replacement of an existing failed timber wall which has already partially been rebuilt (Stop Work due to no engineered drwgs). The wall is about 8' tall at its tallest point. I believe the new construction consists of 6x6 timber facing with timber deadmen. The problem is I'm not very familiar with the design of timber walls of this nature. It seems similar to sheet piling with tiebacks and they may have used a timber pile behind the wall every so often. I've attached a sketch showing what I believe the wall construction will resemble and my assumption of what the analysis should look like. I would appreciate any comments on the sketch as well as any design guides or manuals for walls similar to this.
couple concerns/questions:
Is this type of wall construction acceptable?
How do the deadman anchors' resisting force propagate through the wall (the joints are staggered)? Shear x-fer thru nails is my assumption, but is there a way to calc this or is there a recommended spacing of the anchors?
Thanks again (lots of questions from me this week)?
couple concerns/questions:
Is this type of wall construction acceptable?
How do the deadman anchors' resisting force propagate through the wall (the joints are staggered)? Shear x-fer thru nails is my assumption, but is there a way to calc this or is there a recommended spacing of the anchors?
Thanks again (lots of questions from me this week)?
EIT





RE: Timber Retaining Wall with Deadman
Maybe a better option if you have access to the back of the wall would be to lay in a High Density Polyethylene (HDPE) grid, you'd only need one about 6 feet long, every 2 feet, and you could just attach these between the timber crib boards and you'd have a very nice Mechanically Stabilized Earth (MSE)Wall.
RE: Timber Retaining Wall with Deadman
Thanks.
EIT
RE: Timber Retaining Wall with Deadman
8 ft retained height is not tall enough to warrant a tieback. The design is very similar to that of soldier beam and lagging.
RE: Timber Retaining Wall with Deadman
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RE: Timber Retaining Wall with Deadman
RE: Timber Retaining Wall with Deadman
are you saying that the steel rebar is driven down (vertically) through the timber that is extending back (perpendicular to the wall) into the earth? Is there a way to calculate the resistance that this rebar provides?
EIT
RE: Timber Retaining Wall with Deadman
Yes,steel rebar go trough the timber facing wall, extending into the ground, making an angle of 10 - 20 deg to horizontal plane.
If the ground is not too hard, you can use backhoe to push rebars into the ground.
Frictional resistance of nails can be calculated as driven piles/bored piles, depending on method of nail installation, whether you drill the ground or you push the nails into the ground;
- in clay/silt : fs = alpha x Cu
alpha = 0.7 - 0.8 for pushed nails
0.5 for drilled nails.
- in sand : fs = sigma vert x Ks x tan phi
or 2 N SPT (unit kPa)
RE: Timber Retaining Wall with Deadman
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RE: Timber Retaining Wall with Deadman
I have not design many or any soldier pile walls and only run the calc a handful of times. Normally I would use the California T&S Manual to find embedment required where they use an effective width = 0.08*phi < 3 . However they do not reduce the passive pressure, instead they increase the embedment by %30 percent or so. Is this design method suitable for permanent structures?
Or should I use an effective width = 3*w and reduce Kp by 1.5 or 2? (may end up being similar designs)
Or is it necessary to use a more rigorous design method, any suggestions?
EIT
RE: Timber Retaining Wall with Deadman
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RE: Timber Retaining Wall with Deadman
If you have LPile, you can easily calculate the required embedment and wall inner forces (See the thread by jalthi "Tangent/Secant/Drilled Shaft Wall Modelling in LPile", in this forum).
8' wall is relatively a short wall, and it should be designed as cantilever wall