Retaining wall design: need help
Retaining wall design: need help
(OP)
Hi all,
I'm trying to design a wall retaining a slope of 1:1 slope. Coulomb equation doesn't work in this case; any suggestion?
I'm not familiar with geogrid system. Is this a type of gravity wall? Where can I get info on the design concept?
What is a good ball park figure for angle of friction for both cohesionless & cohesive soil?
For L shape drain design, what are the design considerations? I believed sliding is not a problem, other than overturning, what else should I worry? I can think of bearing failure, settlement & uplifting. How to over come these problems?
thanx in advance
I'm trying to design a wall retaining a slope of 1:1 slope. Coulomb equation doesn't work in this case; any suggestion?
I'm not familiar with geogrid system. Is this a type of gravity wall? Where can I get info on the design concept?
What is a good ball park figure for angle of friction for both cohesionless & cohesive soil?
For L shape drain design, what are the design considerations? I believed sliding is not a problem, other than overturning, what else should I worry? I can think of bearing failure, settlement & uplifting. How to over come these problems?
thanx in advance





RE: Retaining wall design: need help
On reinforced earth, used some times to hold enbankments of your slope, you can find information on
La Ingeniería de Suelos en las Vías terrestres, Volumen 1
Rico - Del Castillo
p. 265
I don't necessarily agree on that Coulomb's can't be used for that. If you want you can use one freely downloadable Mathcad sheet for that using the primary concepts of Coulomb's theory for active push by mere substitution of one more complex definition it has of the surface by straight line slope.
Of course you will have to have a backfill with angle of inner friction going very soundly upwards of your 45 deg to be stable. Otherwise you need more analyzing the stability of your slope than worrying about the retaining wall, for which you have also some sheet isn the collaboratory that help.
Respect typical data for soils I suggest look AASHTO 1992 standard table 5.5.5b
RE: Retaining wall design: need help
There are many companies that supply materials for building mechanically stabilized earth (MSE) retaining walls and reinforced soil slopes (RSS). Having been involved in both design, supply and construction of such wall/slope systems, I can tell you that it is a low-bidder business, and there is substantial risk if you are designing for someone else to supply materials and build the wall. The material supply companies do the design as a cost of selling their products. It will be easier for you to contact them. They are the experts and will essentially give you what you need for the opportunity to sell their products.
RE: Retaining wall design: need help
RE: Retaining wall design: need help
RE: Retaining wall design: need help
RE: Retaining wall design: need help
RE: Retaining wall design: need help
RE: Retaining wall design: need help
My advice to you is to hire a consulting geotechnical engineer to advise and assist you in the design. A geotechnical engineering test boring exploration and analysis is recommended to evaluate the "angle of friction for both cohesionless & cohesive soil" rather than using a "ballpark" values. The test borings and analysis are recommended for the existing on-site foundation soil below the retaining wall, unexcavated retained soils, the backfill soils planned, and the soils planned to construct the 45° slope above the wall. The 45° slope soils will need reinforcement as mentioned in earlier replies. Very few if any soils will be stable with a 45° slope angle without reinforcement. Granular soils for the backfill and 45° slope soils are recommended due to the strength characteristics and construction considerations.
RE: Retaining wall design: need help
Analyze the slope with a friction "circle" methodology, and don't forget global stability.
Now, if the slope is a proposed constructed slope, make the slope fit the area available even if it is steeper than 1:1. I've designed several 1:1 slopes for Ga DOT, FL DOT, and for other clients in NC. I've also designed slopes way steeper than 1:1 for mining clients in WV.
Don't even think about using a segmental block faced wall; even if you use a layer of geogrid every layer of block, over the long term you could still get face destablization. Forget NCMA; their method is ok for walls where supported slopes are 2:1 or flatter, but that is only because the thrust from the slope tends to be kicked down to, or below, the toe anyway.
I would not let the geogrid manufacturers design such a wall; their people tend to be more concerned with moving product than with good design (if they are even capable of it at all - yes, I know this because I once escaped this netherworld)
D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC