Abstract
Dune recovery interventions that integrate natural, sustainable, and soft solutions have become increasingly popular in coastal communities. In the present study, the reliability of an innovative non-toxic colloidal silica-based solution for coastal sand dunes has been verified for the first time by means of laboratory experiments. An extensive experimental campaign aimed at studying the effectiveness of the use of nanosilica has been conducted in the 2D wave flume of the EUMER laboratory at the University of Salento (Italy). The study was first based on a horizontal seabed and then a cross-shore beach-dune profile was drawn similar to those generally observed in nature. Detailed measurements of wave characteristics and observed bed and cross-shore beach-dune profiles were analyzed for a wide range of wave conditions. In both cases, two sets of experiments were carried out. After the first set of experiments performed resembling the native conditions of the models composed with natural sand, the effects of the injection of the mineral colloidal silica-based grout were investigated. The observations show that mineral colloidal silica increases the mechanical strength of non-cohesive sediments reducing the volume of dune erosion, thus improving the resistance and longevity of the beach-dune system.
Highlights
The cross-shore profile of the beach-dune system is measured with the laser profiler in the zone of noticeable profile changes x = 11.0 m–12.5 m (1.5 m onshore distance). This choice stems from the fact that the nanosilica-based grout was sprayed from the toe up to the crest of the dune to evaluate the increase of the erosion resistance exclusively on the dune face
The effectiveness of the use of nanosilica was investigated with two physical models in the 2D wave flume of the EUMER laboratory at the University of Salento (Italy)
The first part of the experimental campaign was carried out on a horizontal seabed to allow us to gain knowledge of the nanosilica properties related to hydrodynamic loadings and effective testing procedures
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. To improve traditional construction techniques that used rock, concrete, and steel, new alternative techniques are proposed, using geosynthetic materials for revetments, scour protection, and reclamation [8] In this regard, planting vegetation and/or constructing plant fences along the backshore was found to be a more natural solution. Historical overviews of the influence of wave conditions, sediment size, sediment gradation, etc., have been extensively studied, for example, by Jonsson [13], Madsen and Grant [14], Sleath [15], Nielsen [16], Fredsøe and Deigaard [17], Van Rijn [18], Soulsby [19], and cross-shore wave mechanics and sediment transport on beaches has been investigated by Nairn and Southgate [20], Kobayashi and Johnson [21], Dean and Dalrymple [22], Tomasicchio et al [23,24], D’Alessandro and Tomasicchio [25], D’Alessandro et al [26], Sancho et al [27], and Brunone and Tomasicchio [28] These works show the wave-induced bottom shear stress as an essential parameter for calculation of beach erosion and accretion rate and wave height attenuation. The conducted experiments, including setup, data analysis, and comparison of the data are presented
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