While planning a retaining wall, it is important to consider the ideal height of the wall, the weight of the soil that it can hold and soil drainage around the wall. Any local building codes that may affect the height of the wall or the materials used in construction should be considered.
Retaining walls encounter immense pressure from heavy soil. Compacting the soil at the base of the retaining wall and directly behind the wall provides a solid foundation for the wall and prevents the wall from bulging out. The builder can use gravel or sandy soil at the base of the retaining wall to improve soil drainage. This is particularly important if the local soil is clay or drains poorly because standing water can weaken the foundation of the retaining wall.
There are three common ways that a retaining wall fails. The first of these is called a blow-out failure. Blow-out failures occur when too much soil is added on top of the retaining wall, which causes the wall to tip forward and eventually fail. The second common failure occurs when soil directly behind the wall becomes saturated with water. The wet soil puts too much pressure on the retaining wall, causing it to bulge or fall. Finally, retaining walls with poor drainage can fail from frost heave. This occurs when water at the base of the wall freezes and expands, pushing the wall up.