

Table 2. Maintenance requirements for shore protection structure 



Type of Structure 



Signs of Failure 



Causes of Failure 



Maintenance or 

 Repair Procedure 



Stone revetment or 



Excessive settlement, increased 



Scour at toe, flanking 



Place additional rock at toe; 



broken concrete 



voids and loss of filter 



undersized stone or 



restore to original elevation 



revetment. 



material, erosion behind or at 



inadequate height. 



section and thickness; reduce 





end of structure. 



improper placement. 



excessive void ratio; back- 

 fill behind structure; 

 extensive upgrading in size 

 of material may be required. 



Gabion revetment; 



Broken wire, excessive move- 



Scour at toe, flanking 



Replace all broken wires and 



stone-filled wire 



ment, erosion behind or at 



excessive strain caused 



reinforce at points of 



mattress. 



ends of structure. 



by displacement. 



severe strain with No. 9 







rusting, and inadequate 



wire ties. 







height. 



Restore structure to original 

 section after each storm; 

 backfill behind structure. 



Sacked concrete, 



Any movement , cracks in 



Subsidence undermining. 



Reestablish support by back- 



slope paving. 



surface, undercut end 



flanking, sliding and 



filling, construction or 



gobi block 



sections, erosion at toe or 



hydrostatic pressure. 



underpinning, and foundation 



paving. 



behind structure. 



inadequate height. 



protection. Reopen weep 

 holes; fill cracks with a 

 suitable sealing material. 



Crib or fence 



Rocking, broken wires or 



Rusting, rotting, theft 



Replace broken and weakened 



revetment. 



members, excessive dis- 



of materials, vandalism. 



wires or mesh as necessary. 



Large concrete- 



placement, erosion behind 



subsidence, flanking. 



Replace missing parts, add 



filled bags. 



structure. 



sliding, and inadequate 



additional cables. These 



Small sandbags. 





height. 



structures are relatively 

 low cost and may require 

 replacement after major 

 storms. 



Groins, steel, 



Loss of fill material, erosion 



Flanking, scouring at 



Fill groins with beach 



concrete, timber. 



behind the groin, and tipping. 



end of structure. 



material; provide riprap toe 







inadequate penetration. 



protection at end of groin. 







Uck of littoral drift. 



Place additional rock at mid 

 point to stabilize structure; 

 add bulkhead at landward 

 end to prevent flanking. 



Seawalls, steel. 



Lakeward movement , erosion 



Loss of foundation 



Reestablish support by under- 



concrete, timber. 



behind at the toe or at the 



support , inadequate 



pinning, tie backs, systems 





end of structure. 



penetration, scour at 



of anchor piling, walers and 







toe, flanking. 



tie rods. Place rock or 







inadequate height. 



rockfilled mattress at toe 

 of structure to prevent scour. 

 Backfill where necessary. 



Offshore break- 



Excessive movement of 



Foundation failure. 



Restore structure to original 



waters, perched 



structure, settling displace- 



undersize stone, 



section. Extensive upgrading 



beach, or jetties. 



ment, or rock-facing material. 



inadequate section. 



in size of material may be 

 required. 



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