Retaining wall types
Retaining wall types
We have detailed numerous retaining wall types including gravity concrete block, inclined concrete block, gabion basket, reinforced concrete block, L shape, concrete criblock, timber criblock and reinforced earth.
Before we begin let’s look at the history of retaining walls. Retaining walls date back to ancient Egypt. They were originally designed to hold back the river Nile. The Nile would flood and erode the soil. The Egyptians built Gabion-style retaining wall from reeds. The walls would divert the flow of the Nile into reservoirs as well as irrigating the fields.
A retaining wall is a structure made from large rocks, baskets filled with small rocks, treated timber, cast in-situ concrete and concrete blocks.
Some of the types are simple to build and others are more difficult. Some have long life spans and others have shorter life spans. Some are economical and some are more expensive.
There are four main types of retaining walls:
- Gravity retaining walls
- Cantilever retaining walls
- Sheet pile retaining wall
- Reinforced soil retaining walls
Gravity retaining walls types
Gravity retaining wall use their mass to act as resistance to hold back the retained earth. To understand the design principles and modes of retaining wall failure read more on retaining wall design.
There are three types of gravity retaining walls :
- Gabion basket
- Concrete block
Gabion basket retaining walls types
Gabion basket retaining walls are constructed by filling wire baskets with stone.
The wire baskets are made of galvanised wire, plastic-covered galvanised wire and stainless steel wire. The baskets are normally 1m x 1m x 2m long.
Concrete block retaining walls types
Concrete block gravity retaining walls are constructed using interlocking concrete blocks.
The concrete blocks are normally 600 x 600mm or 800 x 800mm in width and height and come in various lengths to suite modules of either 600mm or 800mm.
Inclined gravity retaining walls
Inclined gravity retaining walls are similar to gravity retaining walls but they lean into the retaining earth. The angle of the incline is approximately 15 degrees. The incline adds more resistance so fewer blocks are required.
Inclined retaining walls can be made from gabion baskets, concrete blocks and large rocks.
Cantilever retaining walls types
Cantilever retaining walls are l shaped. The long leg of the bottom section is loaded with retained earth or materials. The mass of this earth or material sitting on the base assists the design.
This means fewer materials are required to build the retaining wall. Cantilever retaining walls can be built from:
- Reinforced concrete
- Reinforced concrete blocks
- Reinforced masonry
- Reinforced concrete
L shaped moulds are filled with reinforcement and concrete. The reinforcement is designed to strengthen the joint between the horizontal and vertical sections of the structure and to resist bending.
Reinforced concrete blocks
A raft is constructed and reinforced with top and bottom reinforcement. Starter bars are cast into the raft to connect it to the wall.
The blocks have holes in them to allow reinforcement bars to pass through. On completion of the wall, all the reinforcement holes are filled with non-shrinkable grout.
Steel sheet piles or steel sections are driven into the ground. Approximately one-third of the pile is driven to support two-thirds of the pile to act as the retaining structure. The pile is designed to resist bending and soil failure.
Criblock retaining walls types
Criblock retaining walls are designed in a similar way to gravity retaining walls. They are built with construction frames which are designed to interconnect with each other using notches. The frames come with headers that vary in length 600mm, 900mm, 1200mm, 1500mm and stretchers that are 1.2m and 2.4 m long. There a number of manufacturers for criblock and the sizes of the frames may change from one manufacturer to another.
The frames are filled with stone to add mass as the wall is being constructed. These frames can be built from treated timber, pre-cast concrete or recycled plastic.
Reinforced soil retaining walls types
Reinforced soil retaining walls are constructed using the retained soil. This can only be done if the retaining soil is suitable. Reinforced soil retaining walls are designed by geotechnical engineers.
The retaining structure is built in layers. Each layer is reinforced with a geotechnical reinforcement. This is similar to plastic bunting but is designed to resist tensile forces.
On completion or during construction the face of the retaining wall can be clad with stone or concrete to protect it from erosion.
Very high retaining walls can be built using this method. Criblock and gabion baskets can be used to face the wall as well as concrete blocks.
General retaining wall info
You can see an image of each type of retaining wall at the top of this page. This article is only a general explanation of the different types. You can click the various links within the article to learn more about the topics.
Retaining walls design
Retaining walls are designed by a structural and a geotechnical engineer. The geotechnical engineer gives the structural engineer advice and design data of the soils. The structural engineer then designs the retaining wall to suit the loads and soil type.
For example, the ground bearing capacity is important for the design of the retaining wall. If the ground bearing capacity is weak the structural engineer may make the foundation of the retaining wall wider to spread the load.
We highly recommend retaining walls are engineered to make sure they work. Every retaining wall design is different, head over to the retaining wall design page to learn more about the design process and our services.
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