Experimental investigation on a geocontainer Submerged reef

Abstract

Geotextile sand containers (GSC) have been used as permanent construction elements in coastal works for more than 20 years,becoming more and more popular as an alternative to the most typical coastal structures. Aim of this work is to analyze the hydrodynamic, stability and morphodynamic response of a GSC submerged reef by means of an experimental campaign. The first investigated aspect concerned the hydrodynamics. The reflection and transmission coefficients for regular and random waves were determined: the reflection coefficient decreases with increasing of kh; the transmission coefficient decreases with the increase of the incident wave. As regards the stability of the structure, it was observed that the strongest waves were able to lift the row of GSC more exposed to the wave action. An instability curve for the GSC as a function of the hydrodynamic characteristics was then found. Flow visualization close to the reef was performed by means of ink, showing that the flow becomes asymmetric in the proximity of the structure. Concerning the morphodynamics, long-term tests were performed to calculate the scour. This reached its maximum value at the end of each test and it is present in all three cases. The scour causes serious problems of instability to the structure.