(c) Boring and cutting of piles after treatment should be 

 avoided. Where unavoidable, cut surfaces should receive a field 

 treatment of preservative. 



(d) Untreated timber piles encased in a Gunite armor and properly 

 sealed at the top will give economical service. 



4. Stone . 



Stone used for protective structures should be sound, durable, and 

 hard. It should be free from laminations, weak, cleavages, and undesirable 

 weathering. It should be sound enough not to fracture or disintegrate from 

 air action, seawater, or handling and placing. All stone should be angular 

 quarrystone. For quarrystone armor units, the greatest dimension should be 

 no greater than three times the least dimension to avoid placing slab-shaped 

 stones on the surface of a structure where they would be unstable. All stone 

 should conform to the following test designations: apparent specific gravity, 

 American Society of Testing and Materials (ASTM) C 127, and abrasion, ASTM 

 C 131. In general, it is desirable to use stone with high specific gravity to 

 decrease the volume of material required in the structure. 



5. Geotextiles . 



The proliferation of brands of geotextiles, widely differing in composi- 

 tion, and the expansion of their use into new coastal construction presents 

 selection and specification problems. Geotextiles are used most often as a 

 replacement for all or part of the mineral filter that retains soil behind a 

 revetted surface. However, they also serve as transitions between in situ 

 bottom soil and an overlying structural material where they may provide dual 

 value as reinforcement. The geotextiles for such coastal uses should be 

 evaluated on the basis of their filter performance in conjunction with the 

 retained soil and their physical durability in the expected environment. 



Two criteria must be met for filter performance. First, the filter must 

 be sized by its equivalent opening of sieve to retain the soil gradation 

 behind it while passing the pore water without a significant rise in head 

 (uplift pressure); it must be selected to ensure this performance, even when 

 subjected to expected tensile stress in fabric. Second, the geotextile and 

 retained soil must be evaluated to assess the danger of fine-sized particles 

 migrating into the fabric, clogging the openings, and reducing permeability. 



The physical durability of a geotextile is evaluated by its wear resist- 

 ance, puncture and impact resistance, resistance to ultraviolet damage, 

 flexibility, and tensile strength. The specific durability needs of various 

 coastal applications must be the basis for geotextile selection. 



6. Miscellaneous Design Practices . 



Experience has provided the following general guidelines for construction 

 in the highly corrosive coastal environment: 



(a) It is desirable to eliminate as much structural bracing as 

 possible within the tidal zone where maximum deterioration occurs. 



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