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Civil Engineering : Retaining Walls

Sections: Overview | Retaining Walls | Bridges | Piling | Soil Nailing & Rock Anchors

Retaining Walls

Concrete Retaining Walls

A concrete retaining wall is a structure that retains earth or similar materials. It is mostly used where there is a vertical or nearly vertical change in level.

The most important consideration in proper design and installation of retaining walls is that the retained material is attempting to move forward and down slope due to gravity. This creates a lateral earth pressure behind the wall which depends on the angle of internal friction and the cohesive strength of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes. Lateral earth pressures are typically smallest at the top of the wall and increase toward the bottom. Earth pressures will push the wall forward or overturn it if not properly looked at. Also, any groundwater behind the wall that is not dissipated by a suitable drainage system causes an additional horizontal pressure on the wall.

Concrete retaining walls have gained favour over in-situ concrete walls or timber walls. They are more economical, easier to install and more environmentally sound. There are two methods for fixing the retaining wall in place; embedding them into a concrete floor, or alternatively, using a ground fixing kit. The advantage of the latter solution is that the concrete retaining wall can be moved at a later date.

Gabion Gravity Retaining Walls

Woven Mesh

Rectangular boxes which are formed from panels of ‘triple twisted' mesh which are framed by thicker selvedge wires. End panels and internal diaphragms at 1.0m centers are then wired to the base of the gabion. The triple twist weaving of the wire prevents unraveling.

Welded Mesh

Manufactured from cold drawn steel wire, electrically welded at each intersection welded mesh gabions and mattresses provide an alternative to the traditional woven wire construction. Welded mesh baskets are more rigid and create a more uniform finish when erected, and are appropriate where tight tolerances are required to the finished profile.

Permacrib Gravity Retaining Walls

Permacrib is a timber crib retaining wall system, utilizing the long established gravity wall concept. The patented lightweight interlocking crib components form a series of open cell modules, these are then filled with well graded stone to create the mass required to counteract the earth pressures and surcharge loadings. Structural integrity is achieved through the interaction of the crib elements and the granular infill.