Posted by Kshitija Nadgouda on June 23, 2006
A Retaining Wall is simply a wall that retains (holds back) soil or sometimes water behind it. Here, we will discuss only walls that retain soil behind them. A retaining wall is typically constructed when change in elevation is sudden and requires a vertical (or almost vertical) grade change. The most common example would be along roads in hilly regions. It is not always feasible (economically or due to lack of space) to gradually change the level (elevation) from the road to the hill top and create a slope. In such cases, it is necessary to build a wall that will maintain the hillside behind it (retain the soil) while building a road in front of the wall.
(Courtsey Brockman Engineering Contractors, Inc.)
You can see such walls commonly along the new Mumbai-Pune Expressway and NH-4. The height of the wall may vary from 2 feet to as high as 25 feet. There have been special cases where the height of the wall was as high as 15 m ( roughly 49 feet) for the Ladera Ranch project in California.
Retaining walls can be classified as:
- Cast-in-place concrete walls
- Pre-cast walls
- Modular Block Walls or Segmental Retaining Walls (SRW)
- Mechanically Stabilized Earth Walls
- Other walls such as timber walls, sheet pile walls, brick walls, stone walls, etc
Gravity Walls are typically made from a large mass of concrete and rely only on its self weight to retain the soil behind it. Although more costly than most other options, these are particularly used when the area of soil behind the wall is not enough for reinforcement. These walls are cast-in-place and usually unreinforced.
(Courtsey Concrete Network)
Pre-cast Walls are also typically gravity walls that are assembled on site. Since they are pre-cast, they are used in projects where time is essential.
Modular Block Walls or Segmental Retaining Walls (SRW) are the most extensively used retaining wall type. A SRW consists of interlocking blocks of concrete that are placed over a levelling pad. Since these blocks are available in a variety of sizes, colours, textures, shapes, etc., construction of these walls can be done in the most aesthetic manner even in a cramped space. SRWs being cheap, durable, flexible and easy to install, this are the most preferred retaining wall system used in and around homes for landscaping where the wall heights are typically low.
(Courtsey Tensar Corp.)
(Courtsey Keystone Walls)
Mechanically Stabilized Easth Walls (MSE) are SRWs with typically geosynthetic reinforcements placed within the retained soil. They are primarily a “gravity” type retaining wall, but since they are reinforced with geosynthetics, the effective width and weight of the soil mass that resists overturning or sliding increases greatly. MSE walls utilize the advantages of a SRW for taller walls with structural uses. The 15 m ( roughly 49 feet) wall being built for the Ladera Ranch project in California is a MSE wall.
Most other type of retaining walls such as timber walls, sheet pile walls, brick walls, stone walls are used for non-structural use, such as for landscaping or where these materials are available easily and more economically than other types.
(Courtsey H.B. Fleming)
Copyright Kshitija Nadgouda.