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retaining wall[ri′tān·iŋ ‚wȯl]
a structure that keeps earth lying behind it from sliding.
Retaining walls are used in hydraulic engineering, road building, industrial construction, and civil engineering. They are very common in hydraulic engineering, in which they constitute one of the most important structural elements in embankments, berths, lock compartments, shore abutments of spillway dams and hydroelectric power plants, chutes, and overfalls. They are constructed of natural rock, concrete, reinforced concrete, metal, and wood. The cross-section area and the profile of a retaining wall are determined by calculations of its strength and its shear resistance. When the resistance is provided by its own weight, it is called a gravity-type retaining wall.
A generic structure that is employed to restrain a vertical-faced or near-vertical-faced mass of earth. The earth behind the wall may be either the natural embankment or the backfill material placed adjacent to the retaining wall. Retaining walls must resist the lateral pressure of the earth, which tends to cause the structure to slide or overturn.
There are several types of retaining walls. A gravity wall is typically made of concrete and relies on its weight for stability (illus. a). The mass of the structure must be sufficient to develop enough frictional resistance to sliding, and the base or footing of the structure must be wide enough to develop sufficient moment to resist overturning earth forces. A cantilever retaining wall (illus. b) gains a larger effective mass by virtue of the soil placed on the horizontal cantilevered section of the wall. Reinforced counterforts are spaced along the wall to increase its strength. A variation of the gravity retaining wall is the crib wall (illus. c) is usually constructed of prefabricated interlocking concrete units. The crib is then filled with soil before the backfill adjacent to the crib is placed. Bulkhead retaining walls (illus. d) consist of vertical sheet piling that extends down into the soil and is stabilized by one or more tiebacks and anchors periodically spaced along the structure. The sheet piling may be made of reinforced concrete, steel, or aluminum. See Cantilever
Retaining walls are often used in the marine environment, where they separate the retained soil from the water. Gravity walls (known as seawalls) can be constructed where strong wave and current forces are exerted on the wall. Bulkheads are more commonly found in sheltered areas such as harbors and navigation channels. See Harbors and ports