Retaining Walls Types
Retaining walls Types – We have detailed eight Retaining Walls Types – 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 designed to hold back the river Nile. The Nile would flood and erode the soil. The Egyptians build 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 more difficult. Some have long life spans and other shorter life span. Some are economical and some more expensive.
There are four main types of retaining walls:
- Gravity Retaining Walls
- Cantilever Retaining Walls
- Criblock Retaining Walls
- Reinforced Earth 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 Retaining wall design.
There are three types of gravity retaining walls:
- Gabion Basket
- Concrete Block
- Inclined Gabion and 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 form Gabion basket, concrete block 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 build from:
- Reinforced Concrete
- Reinforced Concrete Blocks
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 a non-shrinkable grout.
Steel sheet piles or steel sections are driven into the ground. Aprroximatle 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 very designed in a similar way as a gravity retaining wall. They are built by construction frames approximately 1m x 1mx x 150mm. The frames are designed to interconnect with each other using notches.
The frames are filled with stone to add mass as the wall is being constructed.
The frames can be built from treated timber, pre-cast concrete or recycled plastic.
Reinforced Earth Retaining Walls Types
Reinforced earth retaining walls are constructed using the retaining earth. This can only be done if the retaining earth is suitable. Reinforced earth 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. The layers are normally 300mm.
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 and to add to the design.
You can see an image of each type of retaining wall above. This article is only a general explanation of the different types. You can click the various links within the article to learn more on the topics.
Retaining Walls Design
Retaining walls are designed by a structural and a geotechnical engineer. The geotechnical engineer gives the structural engineer advise 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.