Transport of Rock on Dynamic Slope Under Oblique Wave Attack
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Published:2018
Gregory Smith, Marcel van Gent, Dennis van Kester, 2018. "Transport of Rock on Dynamic Slope Under Oblique Wave Attack", Coasts, Marine Structures and Breakwaters 2017, Kevin Burgess
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Abstract
For temporary structures or during the construction phase of rock breakwaters it is possible that core material is exposed to wave attack for an extended period of time. For perpendicular wave attack there are methods to predict the profile deformation of dynamic slopes with reasonable accuracy (Van der Meer 1988, 1992). However, when the waves approach at a large angle a combination of cross-shore and longshore transport of the rock will occur. For this situation relatively few prediction methods are available (Mulders, 2010; Alikhani et al., 1996; Van der Meer and Veldman, 1992). To investigate the behaviour of relatively small-sized core material under these circumstances 3D physical model tests have been performed in which the profile development of a dynamic rock slope has been recorded and the longshore transport rate has been quantified by means of photogrammetric measurements. These results have been used to assess the feasibility of this concept for a temporary structure in regions where larger rock is not readily available.
The present study has been performed looking into the feasibility of applying a dynamic rock slope concept as a temporary structure for a region where the only local rock sources are river beds. This means that relatively small-sized (1-50kg), rounded rock would have to be applied. The structure could have a design life from 1 to about 5 years with the purpose of preventing erosion of the hinterland. Therefore, the performance of a dynamic rock slope was assessed for both normally occurring (monthly mean) wave conditions and for more extreme storm conditions. This concept can be applied at any location where the waves approach from one dominant direction. During normal conditions the amount of profile deformation and longshore transport must be assessed to determine the amount of required maintenance. Under a storm condition the crest of the slope should not be breached. Existing calculation methods were applied to determine a conceptual design profile and later that design was tested in a 3D physical model investigation. The goal was to evaluate the feasibility of the concept, in terms of profile deformation and required maintenance.
