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Retaining walls are required in excavations
where the site does not allow for sides to be safely sloped back.
Typically this applies to excavations greater than 8 feet or deeper
in soil or unstable rock.
There are several types of retaining walls
typically used depending on the conditions. In soil, common
retaining walls include H-beam and wood lagging, and soil nailing.
In rock, protection can be as simple as chain link fence to contain
loose rocks or the more positive system or friction rock stabilizers
(split sets) and a shotcrete face.
Top down construction of
retaining walls is the process of completing the exterior or
retaining wall from the top down. The process is usually used in
conjunction with soil nailing or rock nailing. The soil nails serve
the function of tying back the excavation and supporting the
vertical loads of the retaining wall. The advantages include
significant cost and time savings, the flexibility to accommodate
design modifications during construction, and a "one wall"
system that supports construction and provides a permanent wall.
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