Analysis of wave impact on the elastocoast system

Analysis of wave impact on the elastocoast system

Sluijsmans, R.W.

Verhagen, H.J. (mentor)
Van de Ven, M.F.C. (mentor)
Vrijling, J.K. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

2009-09-14

The elastocoast system can be used as an armour layer on revetments. The bonding system exists of a mix of crushed stones and 2-component polyurethane. This bonding system creates bonding forces between the stones and an open (porous) structure can be obtained. Elastocoast is developed by Elastogran GmbH, a BASF subsidiary. The response of an elastocoast layer which is placed directly (without a filter layer) on a geotextile and sand foundation is analyzed in this study from several tests executed in the Large Wave Channel in Hannover. The stiffness of an elastocoast beam is determined in a three point bending test with a dynamic load. The indirect tensile splitting strength and compression strength is determined from several cubes. A model in which the dynamic load of a wave impact event is created (a finite element method program, Plaxis v8, is used) and adapted with the results of all analyzed experiments. The resulting behaviour of the elastocoast layer around the wave impact was predicted according to this model for two cases. First, the elastocoast layer is supported on the foundation over the total length of the layer. Secondly, in case of a gap was formed around the wave impact point in the foundation under the elastocoast layer. The amount and type of the used polyurethaan determines the stiffness of an elastocoast layer. The amount of used polyurethaan increases when an elastocoast beam or cube is formed in a closed framework compared to an layer which of formed on a revetment. The resulting maximum pressure during a wave impact event on top of the elastocoast reduces due to the open structure of elastocoast. The maximum stress inside the elastocoast layer increases significantly when a gap in the foundation is formed. Maximum allowed gap width values in combination with different (regular) wave conditions are shown in several figures in order to avoid breaking of the elastocoast layer due to a wave impact event. The eigen frequency of the elastocoast layer is determined from the vibrations of the layer after each wave impact event. High stresses inside the layer can be expected if it is loaded around the eigen frequency. A static schematization (without dynamic effects) as used in the program GOLFKLAP should not be used in order to determine the maximum stress (or minimum required layer thickness in order to avoid breaking of the layer) inside the elastocoast layer (without a filter layer between the geotextile and elastocoast layer). It is recommended to execute more experiments in order to determine the stiffness and tensile flexural strength from an elastocoast beam with different type and amount of used polyurethaan and with different type and grading crushed stones.

elastocoast
wave impact
golfklap
revetment

http://resolver.tudelft.nl/uuid:f058073d-c46a-442d-84c5-5f6404cd2ba6

2009-09-16

Student theses

master thesis

(c) 2009 Sluijsmans, R.W.