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Cost comparision of an Elastocoast revetment in comparison with a classical revetment in coastal protection.

From 2004 to 2007 several pilot tests with an Elastocoast revetment were constructed along the North-Sea islands in the most northern part of Germany. In 2007 Elastocoast was introduced to the Dutch market. Arcadis supervised the construction and monitoring of two prototype pilots in the Netherlands. (September 2007) Revetment on a rudimentary sea dike called ‘Zuidbout’ near Ouwerkerk in the Eastern Scheldt, 490 m2 on a 1:3-1:4 slope. (October 2007): Refurbishment of the head of beach groyne no. 20.9 near the Pettemer Zeewering along the North Sea coast at Petten, 385 m2 on a horizontal bed. These prototype pilots have been subject to monitoring during the storm seasons of 2007- 2008 and 2008-2009.

ELASTOCOAST revetments are highly porous structures made of crushed stones which are durably and elastically bonded by Polyurethane (PU). To improve the understanding of the physical processes involved in the wave-structure-foundation interaction and to develop prediction formulae for both hydraulic performance and wave loading more than 75 large-scale model tests using both regular and irregular waves were performed. Three ELASTOCOAST revetment alternatives with the same slope (1:3) and the same revetment thickness (0.20 m) but with different thicknesses of the underlying filter layer (0.00 m, 0.10 m and 0.20 m for Model Alternatives A, B and C, respectively) were tested. More than 85 measuring devices synchronously connected to two video cameras were used. Prediction formulae are developed for wave reflection, wave run-up and run-down as a function of the surf similarity parameter which illustrate the advantage of ELASTOCOAST revetments as compared to conventional revetments. For instance, more than 25% less wave runup may result on comparison to smooth impermeable revetments. Using a surf similarity-based wave load classification as well as a systematic parametrization in both time and space, prediction formulae are also developed for both impact loads on and just beneath the revetment. These include the peak pressure pmax, its location in relation to still water level zpmax, the spatial pressure distribution and the time related parameters (rise time and total load duration). Prediction formulae for the wave-induced pore pressure in the sand core beneath the revetment are also provided, including the maximum pressure at the upper boundary of the sand layer and its development in deeper layers. Formulae are also proposed for the flexural displacement ä of the ELASTOCOAST revetment, showing that for impact load much smaller displacements would result than for non-impact load and that ä linearly increases with peak pressure pmax for a given revetment thickness. Finally, a stability analysis of Model Alternative A is performed on basis of the results of the measurements and the simultaneously recorded videos. The results illustrate why Model Alternative failed due to local transient soil liquefaction while Model Alternative B tested synchronously under the same wave conditions did not fail.

In this manual design rules and guidelines for the design of Polyurethane Bonded Aggregate revetments (PBA-revetments) are presented, based on results from laboratory research, full scale model tests, and experience and field measurements. Research is still ongoing, but from the first results some insight into the structural behaviour of PBA can be obtained. For the mechanisms that are most relevant to the design of the PBA-revetment, calculation methods are given to determine a minimum required layer thickness. To account for any uncertainties in the material’s mechanical properties and behaviour, safe assumptions have been used for material parameters. Nonetheless, it is expected from the designer to apply these methods with caution, for each case checking if the assumptions are valid and relevant. Chapter 7 of this manual is dedicated to the remaining uncertainties and the assumptions that have been made. Also recommendations are given to minimize the risk in application of new materials. PBA-revetments are commercially available under the trade name Elastocoast, produced by Elastogran (BASF)