One-way slab acting as retaining wall
One-way slab acting as retaining wall
(OP)
Hello all,
I am assigned the task of designing a replacement retaining wall that is supported by a pile at each end (per project location, and client desire, we could not go about a simple retaining wall w/ footing). The retained soil height is 12'-0" and the span between piles is 11'-6". I am at a loss as to how this slab is to be designed (including the reinforcement), as there is an increasing load from soil pressure. Pile diameter was determined to be 30", and per existing soil conditions each pile is 18'-0" below ground for a total pile height of 30'-0", and the reinforcement cages have also been designed.
Would it be okay to turn the soil pressure into a point load acting 1/3 up from the base of the wall, or is this not correct in this case?
Thank you for your assistance.
I am assigned the task of designing a replacement retaining wall that is supported by a pile at each end (per project location, and client desire, we could not go about a simple retaining wall w/ footing). The retained soil height is 12'-0" and the span between piles is 11'-6". I am at a loss as to how this slab is to be designed (including the reinforcement), as there is an increasing load from soil pressure. Pile diameter was determined to be 30", and per existing soil conditions each pile is 18'-0" below ground for a total pile height of 30'-0", and the reinforcement cages have also been designed.
Would it be okay to turn the soil pressure into a point load acting 1/3 up from the base of the wall, or is this not correct in this case?
Thank you for your assistance.






RE: One-way slab acting as retaining wall
I'm not sure what changes by converting the soil pressure to a point load, you're still going to have the same problems.
RE: One-way slab acting as retaining wall
BA
RE: One-way slab acting as retaining wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: One-way slab acting as retaining wall
No, at a minimum the lowest elevation of the wall needs to be designed for the highest pressure which is at a depth of 12'. The design needs to be conservative, soil pressure can vary from calculated values for several reasons. Also, perhaps a surcharge load will be applied at the surface just behind the wall - say a parked truck, construction equipment, etc.
There is a another issue. A one-way reinforced wall will only be loaded as predicted if the wall is 12' high. The wall should be more than 12' high to prevent soil from raveling under the wall (please see the attached sketch). With the wall embedded in soil there will be some cantilever support of soil behind the wall. Two-way reinforcing is required.
IMHO, the bottom line is don't skimp on wall design - there are too many variables.
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RE: One-way slab acting as retaining wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: One-way slab acting as retaining wall
RE: One-way slab acting as retaining wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: One-way slab acting as retaining wall
RE: One-way slab acting as retaining wall
In the above diagram, the (red) piling resist soil pressure.
The (green) piling, spaced as needed between the red piling, keep the wall from settling when soils are poor.
The horizontal precast concrete members are stacked one-at-time, joint sealed - then backfilled, before placing the next horizontal member.
The photo below, which I took in the 1980's, is one of my father's walls. The horizontal members are salvaged 18" octagonal reinforced precast concrete bridge piling (from the 1930's). The vertical creosoted piling were very used, so have since been replaced more than once. This waterfront bulkhead, now 55 years old, is still in use.
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RE: One-way slab acting as retaining wall
Do secant piling and than Shotcrete the wall to make your waterproof solutions from the inside.
Regards
MSc. Eng. Serguei Joa
Structural Engineer
Bouygues Batiment International, Cuba.
RE: One-way slab acting as retaining wall
However, currently trying to pressure my boss that providing temporary shoring and building a replacement cantilevered retaining wall may make more sense.
RE: One-way slab acting as retaining wall
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: One-way slab acting as retaining wall
From your description of wall damage, looks like the original soil assumptions severely underestimated soil pressure.
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