A retaining wall is an artificial structure which serves to resist the pressure of soil when a change in ground elevation exceeds the angle of repose.
Not only will a well-constructed wall properly support sloping earth, it will also serve as an effective means of draining water runoff and reducing hydrostatic pressure.
The most common of these structures is a cantilever wall, which is a freestanding barrier with no lateral support at the top.
Normally, retaining walls are cantilevered from a footing extending up past the grade on one side and holding back a higher level grade on the opposite side.
They must be planned and constructed to resist pressures from both soil and water.
Another notable type of wall is an anchored retaining wall, which is supported by anchors deep in the earth behind the wall (into the slope).
Soil nailing is a technique that can be employed to further reinforce a retaining wall.
Soil nailing is an economical technique for stabilizing slopes and for constructing retaining walls from the top down.
This ground reinforcement process uses steel tendons which are drilled and grouted into the soil to create a composite mass similar to a gravity wall.
Planning and design is essential when placing retaining walls, recognizing that their sole purpose is to restrict the natural movement of soil down slope due to gravity.
Pressures are lowest at the top of the wall and dramatically increase toward the base.
Improper installation of a retaining wall can lead to tipping or complete collapse due to the differences in force on the wall's surface.
A retaining wall can be constructed using a variety of materials, from stones and concrete blocks, to wood planks and logs.
The height and materials of the wall are determined based on a number of conditions.
Among the most important factors when considering materials and placement are: the proposed height of the wall, the type of soil to retain behind the wall, the angle of the slope, and whether any objects of significant weight are located on the slope (structures, vehicles, etc).
It is also very important to make sure a drainage solution is in place for the soil above the wall.
When the soil absorbs moisture from watering or rainfall, the stress on the retaining wall increase dramatically.
Without proper drainage, the wall will be more susceptible to collapse, sliding or tipping, which can be a very costly and potentially hazardous situation.
By far, the most common uses for these walls are parking lots and driveways, but they can also be used to support outdoor patios or border an in-ground pool.
Whether the property is residential or commercial, sometimes the contours of the landscape limit the options for the path of a driveway, or the elevation and size of a parking lot.
The use of these walls allow driveways and parking lots to exist where it would ordinarily not be possible.
As we all know, functionality doesn't always mean appearance has to suffer.
Stone, concrete and wood (the most common materials for construction of a retaining wall) can nicely accent a property, and also can serve as a foundation for a variety of unique landscaping opportunities that ordinarily would not present themselves.
A wall can be constructed in a series of steps or levels, allowing a unique creative outlet for planting shrubs, flowers, and other decorative elements that will add depth and attractiveness.
Stepped walls have also proven to be a more effective form of erosion control.