On the Stability of Shore-Parallel Geotextile Tubes for Shore Protection

Tubes formed from high strength geotextiles, filled with dredged material or other local sediments, have been used for shore protection in several different configurations. Individual tubes are on the order of 30 feet in circumference and about 6 feet high. Larger or smaller tubes can also be manufactured or the tubes can be stacked to provide higher structures. The tubes are placed either perpendicular to the shoreline as a coastal groin or parallel to the shoreline to protect upland infrastructure against wave action and erosion. Often they are used on the upper beach as the core of a sand dune to provide a last line of defense for upland infrastructure in the event the dune is destroyed by a storm. Tubes have also been used on exposed beaches as emergency shore protection since they can be deployed rapidly by experienced contractors. The location of a shore-parallel tube structure on the beach profile determines its function and the level of wave attack it can experience. Unfortunately, limited data are available to designers on tube stability under wave attack. This paper seeks to develop some of that information for shore-parallel geotextile tube structures located above the still water level (SWL) and subjected to some overtopping. Since toe scour plays a significant role in a tube's stability, laboratory tests and field evaluations of tube performance are needed. This paper presents analyses preliminary to such studies.