Figure 6.4. Retard.
Timber and concrete cribs are sometimes used for bulkheads and retaining walls to hold
highway embankments, particularly where lateral encroachment into the river must be limited.
Cribs are made up by interlocking pieces together in the manner shown in Figure 6.5. The crib
may be slanted or vertical depending on height and the crib is filled with rock or earth.
Reinforced concrete retaining walls are alternatives to timber cribs which can be considered.
However, concrete retaining walls are expensive and are generally only used in special
confined locations where space precludes other methods of bank protection. In constructing
concrete retaining walls, drainage holes (weep holes) must be provided. The foundation of
these walls should be placed below expected scour depths.
Figure 6.5. Concrete or timber cribs.
6.13
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