Definition of a Retaining Wall
Retaining walls are meant to bear the lateral pressure of soil. There are many types of walls but only 04 are considered among the most powerful types of retaining wall.
The Most Powerful Types Of Retaining Wall
Building retaining walls is a fascinating topic. The potential to improve and enhance your property with walls is exciting. But the questions pop into your mind, where do I start?
The more knowledge and information homeowners have about building walls, the more confident they are that their project is being built to the highest standards and that the right wall is being built for their situation.
There are four most powerful types of retaining wall that has been used and improved over time. These types are discussed here.
- Gravity Retaining Wall
- Cantilever Retaining Wall
- Counterfort Retaining Wall
- Buttressed Retaining Wall
Let’s discuss each wall one by one:
Gravity Retaining Wall
Gravity walls are solid, massive, and heavy structures that retain soils using the weight of the wall. The material used to construct gravity walls provides stability against the soil pressing against the back of the wall.
How It Works
Building walls such as gravity walls depends on the conditions at the site. Gravity walls develop their stability from the weight of the wall.
The mass of a gravity wall is usually made up of concrete or stone. The back of the wall (the side in contact with the soil) has a slight batter. The batter is created by making the gravity wall narrower at the top than at the bottom, which improves the stability of the wall.
Easy To Build
These are usually very short and are the simplest to construct. They require less skill to construct than reinforced concrete walls. Gravity walls are also considered the least expensive walls to build, up to four feet.
Design Of Gravity Retaining Wall
The general configuration of a gravity wall is narrow at the top and wide at the bottom. Most gravity walls have a base width that is three-fourths the height of the wall.
2. Cantilever Retaining Wall
The cantilevered wall is a poured concrete wall with reinforced steel bars. The wall has two parts:
a. The stem (the vertical portion of the wall) and
b. The base (the footing).
How It Works
The weight of the soil on the footing helps to resist the sliding and overturning of the wall. The soil resting on top of the footing acts as an integral part of the wall. This weight increases stability without the need for additional concrete, as in the gravity wall.
Design of Cantilever Retaining Wall
The strength of the wall is developed by the steel in the wall and the footing. The steel resists the tensile stress of the soil pressure. The steel ties the stem and the base together to work as a stable unit. Additionally, a wide range of different steel i beam sizes can be used to carry out this project. Accordingly, researching a few different types of steel beams prior to beginning a wall of this nature is strongly recommended.
The stem acts as a cantilever beam supported by the base. The wall transfers the load to the footing behind it. The horizontal force becomes a vertical force as the pressure is directed into the soil under the wall.
The rule of thumb for the width of the base is to build it approximately two-thirds of the height of the wall. A professional engineer determines the quantity and spacing of the steel.
3. Counterfort Retaining Wall
Counterfort walls are usually the tallest type of poured reinforced retaining wall.
Counterfort walls are similar to cantilever walls except they have thin vertical concrete webs at regular intervals along the backside of the wall. These webs are known as counterforts. The webs are on the backside of the wall and covered with the backfill soil.
How It Works
Counterforts tie the stem and the footing together. This reduces the shear forces and the bending moments acting on the wall by the backfill soil. The webs also increase the weight of the wall from the added concrete.
These types of walls are typically made of reinforced concrete. The triangular counterforts are spaced at intervals along the wall.
Design Of Counterfort Retaining Wall
The horizontal steel in the wall transfers soil pressure loads to the webs, which then transfer the pressure to the footing.
Contractors build counterfort walls instead of cantilever walls in order to save money. When a site calls for a wall in the range of 30-feet, a counterfort wall is usually more cost-effective than a cantilever wall.
4. Buttressed Retaining Wall
A buttressed wall is basically identical to the counterfort wall except for one aspect. The webs or the buttresses for the wall are on the outside or front of the retaining wall.
How It Works
The webs are visible to the front of the wall. Therefore, buttressed walls are usually built in areas where aesthetics are not an issue. When used in areas of high visibility, a little imagination in landscaping is needed to make them less objectionable.
Design of Buttressed Retaining Wall
The buttresses add strength and stability to the wall. The soil pressure pushes from the back of the wall, and the forces are transferred to the buttresses.
Buttress walls are designed for projects calling for very tall walls and usually have tremendous loads bearing against the back of the wall.
Before beginning the construction of the most powerful types of retaining wall, consult with a professional engineer about the design of the wall. He will provide engineering plans with details of the wall. The advice of a design professional is the best insurance for a safe and strong retaining wall.