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Sand-filled Geotextile Tubes

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Geotextile tubes or geo-tubes for short, are large tube or sausage-shaped (greater than 2.5m in circumference) geotextiles fabricated from high strength woven geotextile in lengths greater than 6m. These can be used in both coastal and river environments and they are filled hydraulically with slurry of sand and water. An apron of geotextile wider than the geo-tube base may be included as part of the design to protect the seaward edge of the geo-tube from the effects of scouring.  Scour aprons are typically anchored by a small tube at the water’s edge or by sandbags attached to the apron. On the open coast, geo-tubes are laid parallel to shore as a beach or nearshore breakwater with the primary function of limiting the wave height in its lee.  Considering the ‘thumb-rule’ formula for depth-limited wave height;   

 

Wave height, h = 0.8 d        (where d is water depth),  

 

geo-tubes present a sudden limiting condition that cause the larger storm waves from breaking and prevent them from impacting the shoreline.  Geo-tubes have been installed on the threatened shoreline of Tg. Piai in Johor as the first line of defence against waves. 

 

Geo-tube breakwaters are softer than rock armour structures and are visually less intrusive to a mangrove forest environment. In the unlikely event that small boats run into the geo-tubes, it would be akin to running aground on a sandbar as opposed to running into a rock outcrop.