Z55o The bulkheads shown ares 



a. Slab and king pilej concrete (Virginia 



Beach, Virginia) Figure 89 



be Sheet pile| steel (Typical) Figure 90 



Co Sheet pile^ timber (Typical) Figure 91 



These three types are generally interchangeable, though concrete or steel 

 are generally used for higher backfills « 



The revetments shown ares 



ao Stone (Typical) Figure 92 



b» Concrete (Pioneer Pointy Chesapeake Bay, 



Maryland) Figure 93 



2560 Selectio n of TyDCo - The major factors which enter the problem 

 of selection of type arestT) foundation conditions| (2) exposure to 

 wave action? (3) availability of materials| and (ij.) costSo The following 

 paragraph.^ illustrate the manner of review for these factors » 



2^7 o FoT-indation G_ondit ionS o = Fou-ndation conditions have a profound 

 effect on the selection of type of structure to construct, often leading 

 to the adoption of a lEueh more costly type than might be suitable under 

 more favorable foundation conditions « Foundations must be considered 

 from two general aspects o First there is the obvious consideration that 

 the bottom as it exists must be suitable for the type of structure o A 

 structure which depends on bottom penetration for stability could not be 

 used on a rocky bottom<, Generally, random stone or some type of flexible 

 structure involving a stone mat would be used on soft bottom, though 

 a cellular steel sheet pile structure might be used under these conditions- 

 Secondj it should be remembered that the presence of a seawall or bulkhead 

 may cliange the foundation conditions so that^. unless precautions are taken^ 

 a structure might failo Because of induced bottom scour 5 a foundation 

 otherwise stable could become unstable. For example, a masonry wall or 

 mass concrete wall must be protected from the effects of settlement due 

 to bottom scour induced by the wall itself (see Part I)o 



2580 Exposure to Wave Action o = This factor is most ::jnportant in 

 the structural design of any one wall or bulldiead^ and must also be 

 considered in choosing between structural types o For example ^ in areas 

 exposed to severe wave action, the lighter types of structures (timber 

 cribs, light riprap revetment, etCo) may not be usedo Where waves are 

 high, a curved re-entrant face wall might be considered over a stepped 

 face wall, 



259 » Availability of Materials, - This factor would normally be re= 

 fleeted in the costj as generally^ any kind of material can be made 

 available at a price,, In times of shortages and restrictions this does 

 not always hold true and more costly structures have been constructed of 



127 



