There are four main types of retaining wall, which can be created with different materials, and each come with their own advantages and disadvantages.
1. Gravity Retaining Walls
Gravity retaining walls rely on their mass to resist pressure from the load behind, and are therefore made from heavy materials such as stone or concrete. Gabion baskets (steel baskets filled with stones) are an excellent example of this, as they do not require concrete footing, unlike most gravity retaining wall systems. Consequently they are easy to install and simple to remove when required.
2. Sheet Pile Retaining Walls
Sheet pile retaining walls are often used in areas where there is soft soil and tight spaces.
Sheet pile retaining walls are constructed by driving, vibrating or pressing sheet piles into the ground(7.3). A degree of robustness is thus required and in this regard steel is used in the manufacture of the sheet piles.
Anchors to anchored sheet pile walling are typically ground anchors where the anchor comprises a tendon utilising steel bar or strand tendon centrally located in cement grout which can be but not generally injected under high pressure. The cement grout provides the integrity of the anchor and bond between tendon and surrounding soil.
Other forms of ‘tie back’ anchor can be employed utilising screw anchors or ‘dead man’ anchors with associated steel rod or strand ties.
The aesthetic appearance of sheet pile walls can be enhanced by the use of a gabion type facing.
Sheet pile walls can be expensive to install as heavy piling machinery is required, which is often hard to manoeuvre in a small space. As an alternative, gabion baskets of a minimum depth of 300mm can be used in small spaces if held by metal or concrete support posts, but a Consultant engineer will be required to assess the installation.