The natural landscape is never ideally suited to construction as it stands. The earth is just too uneven, before things get built, we always lower or raise the areas of the ground with the help of retaining wall before we built anything. It’s either inconvenient or entirely impossible to use sloped area for building things, walking, driving or even as open spaces like parks. In dense urban area, real estate comes at a premium so it doesn’t make sense to waste valuable land on slopes, where space is limited. It often makes sense to avoid this disadvantage by using a retaining walls to support soil vertically.
What is retaining wall?
A retaining wall is a structure which can hold the earth or any material back to its position so it can prevent the landslide or erosion and make the ground area above and below it usable.
The wall is simply a dam except instead of water, it holds back earth. Soil doesn’t flow as easily as Water but it is twice as heavy. The force exerted on a retaining wall from the soil is called the later earth pressure.
Parts of Retaining Wall:
The wall has basically three parts; stem, toe slab and heel slab. Toe and Heel slab make up for the foundation of the wall. Sometimes key is also provided in some footing to prevent the sliding of the wall.
The stem is provided provided with drain holes with slope for the water drainage. The material which is placed behind the stem is coarse aggregate so that water can easily passes through this drain holes. Heel slab acts as a lever when horizontal force is exerted and help to reduce the overturning of wall.
Forces on A Retaining Wall:
Let us see the different types of forces exerted on the wall. When there is only backfill with no additional load, lateral pressure is applied by the soil. This force will very with the depth of the soil, which means top of the wall will bear no pressure while bottom of the wall bear maximum pressure. It is called a active pressure (Pa).
There is another force act which is called a passive pressure (Pp) which acts from the toe side of the wall and helps a retaining wall.
These are not only the forces exerted, in fact additional forces from buildings, vehicles or other structures on top of the backfill behind the wall. It is called a surcharge load (W), and they can increase the forces on a retaining wall even further. The water passes through it or even freeze in the soil behind it also apply the pressure to its face.
So while designing the retaining wall all these forces can be considered as a civil engineer. Most forces on the other structures are vertical but in the case of the retaining wall they are horizontal.
Types of Retaining Wall:
Now we know that the forces on a retaining wall are horizontal, there are a lot of different types of wall that have been developed to withstand these staggering sideways forces. Let’s walk through a few different designs as discussed below:-
- Gravity Wall : Retaining wall that rely only on their own weight and the weight of the soil above them to remain stable are called gravity wall. The most basic wall which rely on gravity for their stability, often a footing along with base. It more beneficial for the footing to extend inward into the retaining soil. That’s because the the backfill soil sits atop the footing, which acts as a lever arm to keep the wall upright against the lateral forces.
- Cantilever Wall : This wall is a most common types of retaining structure suitable for upto 8 metre of height. The toe, stem and heel are acting as a one way slab and all are act as a cantilever under the different types of forces.
- Counterfort Wall : The counterfort is a retaining structure which have supports called ‘counterforts’ connecting stem and heel slabs. This wall is provided when the height is more than 7 m.
- Buttress wall : Buttress wall is similar to the counterfort Wall but the supports are now on the toe side connecting stem and toe. In the terms of efficiency and economy, the buttress wall is preferred to the counterfort Wall.
Typical Reinforcement in Retaining Wall:
Let’s look at the typical reinforcement In a cantilever retaining wall. The wall is provided with reinforcement to resist the various kind of stresses produced in it.
The main reinforcement is distributed in the stem with the equal spacing along the length. The bars are lapped if required and have 90° hook at the end. The other side of the wall, reinforcement is also provided with the 90° book so proper anchoring is possible. The base slab has reinforcement at both, top and bottom face to resist tension and compression force.
Distribution bars are spread throughout the stem and base slab to resist the stresses and hold the main reinforcement in place as shown in the figure.
Uses of Retaining Wall :-
The different types of retaining walls are used for the types of construction based on the situation. There many uses but following are some of the use case of walls:
- It stabilize the slopes and protect the land.
- Mechanically stabilized earth using geofibers are commonly used on roadway projects.
- Used to protect the exposed soil from erosion due to wind and water.
- It helps temporarily to hold soil back to construct building in dense urban area.
- They are built to construct basements for the high-rise buildings.
Also read,
Hey people!!!!!
Good mood and good luck to everyone!!!!!