Concrete Retaining walls are either cantilever retaining walls or basement retaining walls. The only difference between them is the way the soil is retained. In a cantilever retaining wall, the wall literally cantilevers from the footing while in a basement wall, the wall supports the soil pushing against is by spanning between the footing below and the floor above.
A concrete retaining wall, if designed by a structural engineer and built by an experienced contractor, is by far the most durable type of retaining wall possible. A durable retaining wall also means is a wall that will cost more to build than another type of retaining wall (such as segmented block or CMU), that is the trade off. If you live in San Antonio Texas you’ll have the advantage that concrete is cheap, but still more expensive than using another type of material.
After you have estimated the size of the concrete retaining walll, the next thing is doing a rough estimate of the price the wall. Once you have determined you can afford to embark in this project, the next step is getting a structural engineer to do the actual design of the retaining wall.
The structural engineer will create structural plans (mistakenly referred to as “blue prints”) that will include details that show the dimensions (sizes) of the retaining wall (and the footing) as well as the size, spacing, and location of reinforcement walls for the concrete. The Structural Engineer would also include specifications for the contractor to follow for construction, such as the type of concrete to use. Most importantly, the structural engineer will design the retaining wall with safety as the primary factor.
Another important task that the structural engineer will perform is the general inspection of the construction to ensure that what is being built actually matches what’s in the structural plans. This is a very good quality control service that helps the owner, contractor, and the engineer himself as well.
The construction of the concrete retaining wall is not easy, an experienced contractor is preferred.
The construction would begin with excavation of some sort; usually the retaining wall goes in a spot where the terrain grades are uneven so the soil needs to excavated. The retaining wall may also be designed with some type of select fill (i.e. some good soil) behind it, so excavation beyond the back of the wall is necessary. Usually, the amount of select fill behind the wall needs to be at least the same as the height of the wall including the footing thickness. So if the wall is 9 feet tall and the footing is 1.5ft thick, then 10.5ft behind the retaining wall would be select fill. However the amount of excavation may be more to make place for the width of the footing.
After excavation there’s compaction of the soil where the footing will be resting, unless the soil supporting the footing foundation is rock. If it’s a loose soil and no compaction is done, the footing may settle and the wall may overturn.
Then you need to form the thickness and width of the footing with some wood forms. Sometimes parts of the footing are into the ground so the amount of forming can be reduced. After the forms are ready, you start laying out the rebar for the footing foundation, as well as the dowels that will go into the wall.
The footing then gets poured (but prior to being poured, the structural engineer would have seen that the rebar and everything else matches the construction plans). After the footing is poured, the only thing you should be able to see is the bars sticking up (the dowels) where the retaining wall will be. The footing should be allowed to cure (i.e. harden) until the strength of the concrete has reached at least 75% of its design value, which usually occurs after 7 days from pouring concrete.
Once the concrete has reached 75% strength, then the forms for the retaining wall are set on top of the footing along with all the reinforcement for the wall. The concrete is poured and the forms are left in place (and properly braced) until the concrete has reached full capacity.
After removing the forms for the retaining wall, the back of it is filled with good soil (select fill) and voila, you now have a full functioning retaining wall.
We hope this article was very helpful to you and if you have any more questions or need help on your next project, please do not hesitate to Structural Engineer San Antonio for more info.and please visit our