Geotextile forms for sand structures

The use of sand for the construction of dams and dikes, sand closures, artificial islands, beach nourishment, etc. is a common Dutch practice in hydraulic and coastal engineering.Dutch experience with the application of sand as a construction material,including design and execution aspects,is well-documented and can be found in the following evaluation reports ( CUR, 1987 , 1992a,b ). The use of sand outside of the Netherlands is usually limited to beach nourishment (deposition of flat beaches). Other applications of sand for the construction of coastal and marine structures have always been met with a certain scepticism, possibly due to its fine consistency (fine grains) and low resistance to waves and currents. The main weak point when using sand, especially when it is transported and placed hydraulically, is the very mild slope of placed sand. The slope gradient depends on the ratio of sand-water mixture and the grain size. Coarser grains result in steeper slopes. Usually, the slopes are in the order of 1 on 20 to 1 on 100 above water and 1 on 10 to 1 on 50 under water. These mild slopes usually require a huge amount of sand to be built. Moreover, hydraulic deposition of sand induces a high rate of sand loss.