SAND TUBES (LONGARD TUBE} 



Sand tubes on Thybor^n Barrier Beach, 

 North Sea coast , Denmark . 



Prototype Installation : 



Thybor^n Barrier, North Sea coast, Denmark. 



Sand pumped into nylon tubes . Structure is three tubes , each 

 1-meter diameter and 100 meters long laid parallel to the beach 

 above the waterline (Jakobsen and Nielsen, 1970) . 



Empire Village, Lake Michigan, Michigan. 



A 4 2- inch -diameter Longard tube was set on filter cloth parallel to 

 shore and filled with sand. Actual project cost was $28.30 per lineal 

 foot of shore (Brater, Armstrong and McGill, 1974). 



Wave Tank Tests : 

 Unknown . 



Design Factors : 



Zero-damage wave height: Unknown. 



Wave runup: 0.8 to 0.9 compared to smooth slope (estimated). 

 Wave reflection: High (estimated). 



Remarks : 



An apron or other suitable toe protection would be needed to prevent 



toe scour. 



Tube could also be used as groin or offshore sill. 



Structure could be easily damaged by vandalism or drifting debris. 



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