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shows a rubble-mound seawall. The stone protecting the shoreline against erosion is called riprap. There- fore, a rubble-stone seawall is called a riprap seawall. Various types of cast-in-place concrete seawalls are  the  vertical-face,  inclined-face,  curved-face, stepped-face,   and   combination   curved-face   and stepped-face. The sea or harbor bottom along the toe (bottom of the outside face) of a seawall is usually protected against erosion (caused by the backpull of receding  waves)  by  riprap  piles  against  the  toe. Groins Groins, built like breakwaters or jetties, extend outward from the shore. Again, they differ mainly in function. A groin is used where a shoreline is in danger of erosion caused by a current or wave action running obliquely  against  or  parallel  to  the  shoreline.  It  is placed to arrest the current or wave action or to deflect it away from the shoreline. Groins generally consist of tight sheet piling of creosoted  timber,  steel,  or  concrete,  braced  with  wales and with round piles of considerable length. Groins are usually built with their tops a few feet above the sloping  beach  surface  that  is  to  be  maintained  or restored. Bulkheads A bulkhead has the same general purpose as a seawall:  to  establish  and  maintain  a  stable  shoreline. But, whereas a seawall is self-contained, relatively thick, and supported by its own weight, a bulkhead is a relatively thin wall supported by a series of tie wires Figure 10-26.-Timber bulkhead for bridge abutment. or  tie  rods,  running  back  to  a  buried  anchorage (deadman).  A  timber  bulkhead  for  a  bridge  abutment is 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 sheet piles, an example of which is shown in figure 10-27. The outer ends of the tie rods are anchored to a steel wale  running  horizontally  along  the  outer  face  of  the bulkhead. This  wale  is  usually  made  up  of  pairs  of  steel channels bolted together, back to back. A channel is a structural  steel  member  with  a  U-shaped  section. Sometimes the wale is placed on the inner face of the bulkhead, and the piles are bolted to it. The anchorage shown in figure 10-27 is covered by 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 buried sheet piles. A more substantial anchorage for each tie rod  is  used  below  the  groundwater  level.  Two common  types  of  anchorages  are  shown  in  figure 10-28.  In  view  A,  the  anchorage  for  each  tie  rod consists of a timber cap, supported by a batter pile. In view  B,  the  anchorage  consists  of  a  reinforced concrete cap, supported by a pair of batter piles. As indicated in the figure, tie rods are supported by piles located  midway  between  the  anchorage  and  the bulkhead. Bulkheads   are   constructed   from   working drawings like those shown in figure 10-29. The detail plan  for  the  bulkhead  shows  that  the  anchorage consists of a row of sheet piles to which the inner ends Figure 10-27.-Constructed steel sheet pile bulkhead. 10-14

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