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Inclined retaining walls

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Inclined retaining walls – Rampsbeck hotel

We were approached by a contractor to value engineer an inclined retaining wall. The original design was an inclined gabion basket retaining wall. We reviewed the levels and redesigned the structure using interlocking concrete blocks. The contractor wanted a fast build and the gabion solution was slow.

The diagram below shows the profile of the bank. We designed a wall to retain the earth using the profile. The contractor provided us with a site investigation report. The ground bearing capacity was 100kN/m2. This gave us a few issues as the mass of the wall was causing failure with this constraint. We designed the first two courses of blocks to be reinforced into the raft. We then made the raft slightly larger than our standard design to ensure the design worked.

Inclined retaining walls built using concrete blocks are very competitive as they use less blocks than standard gravity retaining walls. The incline with the aid of gravity gives a little more resistance to the forces.

 

Rampsbeck 3

The table below is our standard wall heights and foundation design. This table gives you some idea of what is possible. The example above proves that all walls need to be checked to ensure they work with the local ground investigation information.

Inclined retaining walls

Retaining wall design and price guide

We have free design and price guide to support contractors and engineers with different types of retaining wall types and designs. Click on the link below and download your copy. It’s essential reading and may give you some ideas for your next project.

Download the design and price guide

Click here to learn more about inclined retaining walls.

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Flood defence

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Flood defence solutions to project water works

We had an enquiry recently to protect a waterworks plant from flooding. The waterworks had been built on a flood plain. The site was sloping so we worked out the flood risk flooding height and designed a wall to protect the plant. The general arrangement of the design is shown on the image above.

We used our standard wall type. the wall heights ranged from 900mm to 2100 mm. The image shown on the page is the 2100 mm wall.

The wall is constructed using two skins of 300mm concrete interlocking blocks with a waterproof membrane in between to stop water from passing through the joints. The wall is then capped off using a 600mm wide x 300mm deep coping. The coping ties the wall together at the top.

The wall is built on a concrete foundation. The outer skin of wall is dowelled into the foundation to give stability during flooding.

Floodplain map

To find out the risk of your building assets you can go to the floodplain map the environmental agency has developed. The link to the site is Floodplain Map. From this page read the content and then click on the map. You can zoom in to your location or locations and see if your building assets are at risk. This is the first step of an assessment. If you are at risk the next step is to work out how high the flood water could rise. You can then design a flood defence system to protect your building assets in the case of flooding is your area.

Retaining wall design and price guide

We have a free design and price guide to support contractors and engineers with different types of retaining wall types and designs. Click on the link below and download your copy. It’s essential reading and may give you some ideas for your next project.

Download the design and price guide

Click here to learn more about flood defence walls.

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Cantilever retaining wall

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Cantilever retaining wall using concrete interlocking blocks

We have designed a cantilever retaining wall built from concrete interlocking blocks. The blocks have ducts that pass through the blocks. We pass reinforcement bars through the ducts to tie the blocks together and connect the wall blocks to the foundation. The foundation together with the block wall act as a cantilever retaining wall.

The height of the wall, the size of the foundation and the details of the reinforcement can be taken from our design table below. The design table has design assumptions so we recommend that every retaining wall is analysed to ensure they work. The main design variables are ground conditions and any surcharge load.

Cantilever retaining walls design table

The table below has been developed to help you value engineer your retaining wall. We would recommend that you  download our retaining wall design guide. This will allow you to compare costs of each type of retaining wall we build.

The design table below presents indicative designs based upon a base material with allowable bearing pressure of >200kPa.

The retained material is assumed to be well graded, granular backfill with back of wall drainage or weep holes to relieve hydrostatic pressure.

All indicative information presented in this table is based upon assumed loading and ground conditions and may be subject to change following detailed, site specific design.

Cantilever Retaining Wall

Patent pending

Our design concept of reinforced interlocking concrete blocks is an original idea we have filed a patented. The patent is now pending. The patent has been filed by Virtus Concrete Solutions Ltd our block supply partner.

Retaining wall design and price guide

We have a free design and price guide to support contractors and engineers with different types of retaining wall types and designs. Click on the link below and download your copy. It’s essential reading and may give you some ideas for your next project.

Download the design and price guide

Related articles

Below you will find links to related articles:

How to build a reinforced retaining wall
Retaining Wall Design

KNOWLEDGE BASE

How to build a reinforced concrete block retaining wall

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How to build a reinforced concrete block retaining wall

Watch the video below to learn how to build a reinforced concrete block retaining wall. It will explain the design principles and will go through the process step by step.

This type of retaining wall is very easy to build and is economical compared to many other construction methods.

It uses less blocks than gravity block retaining walls.

You can compare the various cost for different types of retaining wall by reading our retaining wall design and price guide. Click here to download a copy.

The design process

The process to design a retaining wall is as follows:

Work out the project scope – What is the wall being designed to do and what are the load cases.

Determine the soil conditions – We need to understand the material that is being retained and the material the structure is sitting on. If the wall is retaining existing soil we need to understand the soils characteristics. Is it sandy-type soil or clay-type soil? What is the bearing capacity of the soil the wall is being founded on?

Check for sliding – We will design the wall and carry out a number of checks to ensure the wall works. The first check is to make sure the wall does not slide.

Check overturning – The second check is to make sure the wall does not overturn.

Check bearing capacity – We check the ground bearing capacity can take the loads from the structure.

Complete structural design – Once all the checks are made we then complete the structural design making sure the correct amount of reinforcement and concrete is specified.

Retaining wall engineering service

We can offer the following services:

  • Ground investigation
  • Retaining wall design including calculations
  • Development of working drawings and reinforcement schedules

Every project is different so we can only provide prices from a detailed conversation with you. Good ground conditions data is critical for the correct design of a retaining wall.

We can offer the following services:

  • 2D and 3D drawings of the walls
  • Wall design including calculations
  • Development of working drawings and reinforcement schedules.

Every project is different so we can only provide prices from a detailed conversation with you. Book a call today.

Ask a question

Complete the form on our contact us page to ask a question. We normally answer questions and respond within 24 hours.

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Retaining wall types

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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
  • Masonry

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
  • Piles
  • 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.

Piles

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.

Ask a question about retaining walls types

Complete the form on our contact us page to ask a question about retaining walls. We normally answer questions and respond within 24 hours.

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Retaining wall construction

Retaining Wall Construction

Retaining wall construction wall types

There are a number of wall types you can construct:

There are many ways and methods of building a retaining wall. It all depends on the retaining wall type.

The example below is for the construction of a reinforced block retaining wall. The design is based on cantilever principles. The wall is connected to the foundation and looks like an L shape. The retained earth sitting on the foundation helps the retaining wall design properties.

The alternative to this design is a gravity retaining wall, but this uses more blocks.

Retaining wall construction design

Before you can build the retaining wall, it needs to be designed. Normally some ground investigation data is required for the retained earth and the ground bearing pressure. This can be done by excavating trial excavations and giving the information to a structural engineer who will design the wall. For more information about getting the right soil information go to our design page and watch the video.

The design of the wall will look similar to this design drawing. You can look at our reinforced block design guild table for more information. The tables have been designed for costing purposes, the design for your project may be different depending on the soil type.

Retaining Wall Design Drawing

Step 1 – Excavation

Excavate the surrounding area in preparation for the retaining wall. Ensure the formation ground is firm. Lay 50 to 100mm of blinding concrete over the formation to give a flat and level surface. This also protects the formation and stops any contamination of the reinforcement.

Step 2 – Formwork

Place formwork for the raft. Ensure there is 40mm of cover for the reinforcement. The reinforcement type and size will depend on the size of the structure and the design.

Step 3 – Reinforcement

Fix the starter bars in position. It is important that they are placed accurately. To do this fix supporting timbers from the edge formwork as shown. Depending on the size of the block the centres will be either 600mm or 800mm. The dimension from the face of the wall to the bar location is 450mm for 600mm blocks and 650mm for 800mm blocks.

How to Build a Retaining Wall Step

Step 4 – Concrete

Pour concrete into the formwork. Make sure the started bars are not moved. It is worth checking to starter bars before the concrete sets.

Level the concrete to the top of the formwork and leave with a light tamp finish.

The strength of the concrete will be given by the design but is normally a C40 mix.

Step 5 – Constructing the first layer

Lay the first layer of blocks. Place them over the started bars. On completion of the first layer, lay the back drainage pipe. It is important that any water behind the wall is taken away to stop hydrostatic pressure from building up.

This is done by laying a perforated pipe and backing filling with clean stone to act as a filter. The clean stone fill can be wrapped in geotextile to filter out any fine particles from the soil that will eventually block the stone filter.

How to Build a Retaining Wall Step 7

Step 6 – Compete the construction

Build the wall to full height and backfill with clean stone and retained earth as you go.

Fit the vertical rebar to the design and grout in using a non-shrinkable grout. This is important for the structural stability of the completed wall and to stop the rebar from corrosion.

Step 7 – Watch the video for more detailed.