Retaining Walls

 Gravity Retaining Walls

Ø  Gravity walls depend on their mass (stone, concrete or other heavy material) to resist pressure from behind and may have a 'batter' setback to improve stability by leaning back toward the retained soil.

Ø   For short landscaping walls, they are often made from mortar less stone or segmental concrete units (masonry units).

Cantilevered retaining walls

Ø  Cantilevered retaining walls are made from an internal stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T).

Ø  These walls cantilever loads (like a beam) to a large, structural footing, converting horizontal pressures from behind the wall to vertical pressures on the ground below.

Counter fort/Buttress on Cantilevered Wall

Ø  Sometimes cantilevered walls are buttressed on the front, or include a counter fort on the back, to improve their strength resisting high loads. Buttresses are short wing walls at right angles to the main trend of the wall.

Ø  These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall.

Sheet pile wall

Ø  Sheet pile retaining walls are usually used in soft soils and tight spaces. Sheet pile walls are made out of steel, vinyl or wood planks which are driven into the ground. For a quick estimate the material is usually driven 1/3 above ground, 2/3 below ground, but this may be altered depending on the environment.

Ø  Taller sheet pile walls will need a tie-back anchor, or "dead-man" placed in the soil a distance behind the face of the wall, that is tied to the wall, usually by a cable or a rod.

Ø  Anchors are placed behind the potential failure plane in the soil.

Anchored retaining wall

Ø  An anchored retaining wall can be constructed in any of the aforementioned styles but also includes additional strength using cables or other stays anchored in the rock or soil behind it.

Ø  Usually driven into the material with boring, anchors are then expanded at the end of the cable, either by mechanical means or often by injecting pressurized concrete, which expands to form a bulb in the soil.

Technically complex, this method is very useful where high loads are expected, or where the wall itself has to be slender and would otherwise be too weak.

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