Retaining wall as the name itself suggests is used to retain lateral soil pressure or hold back soil materials. These walls are structures that are designed to resist the lateral pressure of soil especially when there is a change in ground elevation – natural or otherwise. These are designed in a way that the pressure is resisted at various levels on either side.
Such retaining walls are used for supporting soil in a sloping manner which otherwise is not possible. Such walls are typically used in regions with slopy terrains or in construction sites where the landscape needs to be changed intensively for mountain farming or to construct roadway overpasses and bridges.
The main purpose of a retaining wall is to impede soil or other material from collapsing or slipping as well as preventing erosion. It is designed in a way that it can withstand the intense continuous pressure exerted by the material whose angle of repose is exceeded which otherwise would collapse in its natural form. In such cases, the lateral pressure caused by the material on the retaining wall is practically zero at the top of the wall while the pressure at the lowest depth of the wall is maximum.
In the majority of cases, it is also essential to have an effective drainage system behind the wall to eliminate or at least reduce hydrostatic pressure. Hence, according to the guidelines provided by the International Building Code, retaining walls should be designed and constructed in a way that they ensure stability against overturning, sliding, excessive foundation pressure and water uplift. They should also provide a safety factor of 1.5 in case of lateral sliding and overturning.
Types of Retaining Walls
There are various types of retaining walls out of which three of them are mentioned here. Choosing the right one depends on the location, type of soil and its purpose.
Gravity Retaining Wall
Gravity walls depend on their mass to resist lateral soil collapse. As these walls tend to hold against pressure through their weight, they are usually constructed of heavy materials like stone, large concrete blocks, etc. In cases where stones are not used, interlocking concrete block moulds are used to create large blocks. They are usually straight or slightly curved rising to 4 feet but the height may vary depending on the purpose and design value.
Cantilevered Retaining Walls
Built by using concrete, these walls have a base and use the principle of leverage and hence, they are often designed in the shape of an inverted ‘T’. they are one of the most commonly used retaining walls and are usually made of a lot of sand and a slab foundation loaded with backfill to support the pressure on the wall.
Buttressed Retaining Walls
Also known as counter-fort walls, these walls are majorly used in dam construction. Think of it as a cantilever retaining wall but with the extra support of concrete webs or counterforts built in a sloping manner to strengthen and retain the pressure. They are high retaining walls capable of handling high pressure.