shows a rubble-mound seawall. The stone protectingthe shoreline against erosion is called riprap. There-fore, a rubble-stone seawall is called a riprap seawall.Various types of cast-in-place concrete seawallsare the vertical-face, inclined-face, curved-face,stepped-face, and combination curved-face andstepped-face. The sea or harbor bottom along the toe(bottom of the outside face) of a seawall is usuallyprotected against erosion (caused by the backpull ofreceding waves) by riprap piles against the toe.GroinsGroins, built like breakwaters or jetties, extendoutward from the shore. Again, they differ mainly infunction. A groin is used where a shoreline is in dangerof erosion caused by a current or wave action runningobliquely against or parallel to the shoreline. It isplaced to arrest the current or wave action or to deflectit away from the shoreline.Groins generally consist of tight sheet piling ofcreosoted timber, steel, or concrete, braced with walesand with round piles of considerable length. Groinsare usually built with their tops a few feet above thesloping beach surface that is to be maintained orrestored.BulkheadsA bulkhead has the same general purpose as aseawall: to establish and maintain a stable shoreline.But, whereas a seawall is self-contained, relativelythick, and supported by its own weight, a bulkhead isa relatively thin wall supported by a series of tie wiresFigure 10-26.-Timber bulkhead for bridge abutment.or tie rods, running back to a buried anchorage(deadman). A timber bulkhead for a bridge abutmentis shown in figure 10-26. It is made of wood sheathing(square-edged, single-layer planks), laid horizontally.Most bulkheads, however, are made of steel sheetpiles, an example of which is shown in figure 10-27.The outer ends of the tie rods are anchored to a steelwale running horizontally along the outer face of thebulkhead.This wale is usually made up of pairs of steelchannels bolted together, back to back. A channel is astructural steel member with a U-shaped section.Sometimes the wale is placed on the inner face of thebulkhead, and the piles are bolted to it.The anchorage shown in figure 10-27 is coveredby backfill. In stable soil above the groundwater level,the anchorage may consist simply of a buried timber,a concrete deadman, or a row of driven and buriedsheet piles. A more substantial anchorage for each tierod is used below the groundwater level. Twocommon types of anchorages are shown in figure10-28. In view A, the anchorage for each tie rodconsists of a timber cap, supported by a batter pile. Inview B, the anchorage consists of a reinforcedconcrete cap, supported by a pair of batter piles. Asindicated in the figure, tie rods are supported by pileslocated midway between the anchorage and thebulkhead.Bulkheads are constructed from workingdrawings like those shown in figure 10-29. The detailplan for the bulkhead shows that the anchorageconsists of a row of sheet piles to which the inner endsFigure 10-27.-Constructed steel sheet pile bulkhead.10-14
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