Geogrid with Boulder Retaining Wall?
Geogrid with Boulder Retaining Wall?
(OP)
Is it industry custom and practice to use a geogrid in the construction of a boulder retaining wall with a height of approximately 6' or higher?
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Geogrid with Boulder Retaining Wall?
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Geogrid with Boulder Retaining Wall?Geogrid with Boulder Retaining Wall?(OP)
Is it industry custom and practice to use a geogrid in the construction of a boulder retaining wall with a height of approximately 6' or higher?
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RE: Geogrid with Boulder Retaining Wall?
RE: Geogrid with Boulder Retaining Wall?
RE: Geogrid with Boulder Retaining Wall?
The base width of the wall constructed of rocks, carefully placed in a brickwork fashon was designed as a gravity wall. The backfill was always fine shot rock in the minus 12 inch size with the coarser rock placed closest to the wall. I did walls up to 30 feet high supporting condos.
In the late 1990's we added geogrid with only a single facing rock width. We only use HDPE because the backfill (fine shot rock) can easily damage polyester grids. We used a relatively high reduction factor for damage and generally didn't use anything smaller than UX1500.
This is an economical retaining wall where there is a large cut and fill required in granitic bedrock.
RE: Geogrid with Boulder Retaining Wall?
For these "boulder walls" its not always easy to make the calculations stack up, especially with respect to strength at the connection with the "facing." The best you can hope to do is figure out what contact area you need to get 100% of the factored design tensile stress (since you'll never get 100% of Tal of the grid, use what's needed not what's available) and specify the contact area in the construction spec.
In summary, its not entirely conventional, but it works and you should be able to figure out a way to make it work on paper as well.
A final word - over 6' and less than 20' is probably okay but I'd start to sweat a bit higher than 20'.
RE: Geogrid with Boulder Retaining Wall?
RE: Geogrid with Boulder Retaining Wall?
I believe this is the manual you are talking about.
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RE: Geogrid with Boulder Retaining Wall?
RE: Geogrid with Boulder Retaining Wall?
Industry standard per NCMA and FHWA is to consider geogrid for anything higher than 4 feet and include geogrid for anything higher than 6 feet. That is the industry standard. There are some larger block that can go higher, just make sure the gravity mass is properly designed.
RE: Geogrid with Boulder Retaining Wall?
Thanks for any input.
Mike McCann
McCann Engineering
RE: Geogrid with Boulder Retaining Wall?
i'm not familiar with the "Ecology Block".
This thread discusses the use of arranged boulders for the facing, which causes a problem with designing in geogrid, because the connection between boulders is not an engineered joint that can serve as the mechanical connection,... Or can it.... We've been wrestling with this point with boulders on a current project. We gave up on really engineering it and looked for other ways to reduce the wall height so we could use the FHWA documents as a guideline.
I looked at a photo of a "ecology block" in wikipedia and it seems similar to some blocks i've used. Try taking a peek at www.redi-rock.com and see if these materials are similar to what you're interested in. The website has sample designs with some of the comps for a large variety of different large concrete blocks (reinforced and unreinforced) and in different loading conditions and soil conditions.
RE: Geogrid with Boulder Retaining Wall?