Rock Slopes With Open Filters Under Wave Loading: Effects of Storm Duration and Water Level Variations

Abstract

Rubble mound breakwaters and revetments typically contain granular filters in one or more layers. The transition from the armour layer to the filter layer, and transitions between other layers within the structure, are normally geometrically tight to prevent material washout. This requires a limited ratio of the material size of the upper layer and neighbouring layer. An alternative is a geometrically open filter where in principle underlayer material can be transported into the upper layer, but if the hydraulic load at this transition between two layers remains low, the transition can be designed such that no or limited transport occurs, see for instance Van Gent and Wolters (2015), Van Gent et al (2015) and Jacobsen et al, (2017). This allows for larger ratios of material sizes, which can reduce the number of filter layers, and relax the material requirements with respect to the width of gradings. This can lead to considerable cost savings. In Van Gent and Wolters (2015) physical model tests for the transition between a layer of rock and an underlayer that consists of sand have been performed and design guidelines have been derived. Here, additional physical model tests are presented to study the influence of the storm duration and water level variations on the response of sand underneath a layer of rock.

The effect of variations in water level on wave overtopping discharge over a dike: An experimental model study

“…In literature, based on the authors' knowledge, only two experimental campaigns have investigated the role of water level variation: on armour stability (Van Gent et al, 2016 and on wave overtopping (Kerpen et al, 2020). Marzeddu et al (2020) were used to assess the damage response of a rock armoured dike (slope 1:3) due to the variations in water level during a simulated storm.…”

Effects of Water Level Variations on the Stability of Rock Armoured Slopes

“…However, in reality water levels vary during the peak of a storm due to the presence of storm surge and/or a tide. Coastal structures can also experience an accumulation of damage to the armour layer due to various storms, while each of the storms can occur at a different water level (see for instance Melby andKobayashi, 1998, for armour layers andVan Gent et al, 2016, for effects of water level variations on material underneath the armour layer). In contrast to most physical model tests performed in the past, here tests have been performed with rock armoured slopes ( Figure 1) with wave loading under various water levels, including tests with water levels that continuously vary during a single experiment, resembling a tide (Figure 3; lower right panel).…”