Washington State Department of Ecology
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retaining walls
retaining wall on Puget Sound
Competent retaining wall construction is crucial. Inadequate designs can fail.

Gravity structures, such as rock walls or crib walls, rely on their own weight to counter slope movement. Cantilevered structures are anchored to stable soils that underlie slide material. Other types of retaining structures include tie-back walls and reinforced earth embankments. Retaining structures can be placed at the base, middle, or near the top of a slope, depending on the nature of the potential landslide and the type of wall.

Good engineering is critical
Retaining structures can be extremely expensive, requiring good engineering design work, high quality materials, specialized equipment, and often difficult site access. Competent design is crucial. Failures of retaining walls are relatively common and repairs can be far more expensive than original work.

Adequate drainage is important
Problems often occur when water builds up behind an improperly drained structure, putting excessive loads on the wall or weakening the structure or when the structure is inadequately designed and a deeper landslide causes the entire slope, including the wall, to fail.
retaining walls need adequate drainage
 
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