Until now, an extensive design method for mild slopes has not been available. The aim of this thesis is to understand the stability of rock on mild slopes under wave attack for impermeable cores in order to optimize designs. Physical model tests have been executed to study this stability for a 1:8 slope. Mossinkoff (2019) executed physical model tests for a 1:10 slope and a re-analysis of these tests is included in this thesis as well. Damage caused by entrained rocks is quantified by damage parameters using stereophotogrammetry and coloured rocks in strips. In this study, the influence of several hydraulic and structural parameters on damage parameters has been investigated for mild slopes. A positive correlation has been found between the significant wave height and the damage parameters. Besides this, based on the analysis it can be concluded that the wave steepness and damage parameters are negatively correlated. An increase in layer thickness of the rocks does not seem to increase the stability of rock on mild slopes. However, the slope angle does have an effect on the stability as a milder slope is associated with less damage. Another conclusion is that more damage continues to be observed even after 15 000 waves. Based on the results of the physical model tests, a design formula is developed for mild slopes to be able to increase efficiency in designs of coastal structures for these mild slopes. This study also provides evidence that rocks on mild slopes have different characteristics of damage and damage development compared to steep slopes. The largest share of entrained rocks transport in upward direction and rocks on mild slopes seem to be more mobile compared to steep slopes. This suggested that it might be more efficient to study the moment when the filter layer or the core becomes visible instead of the static stability of rock within the armour layer itself. ... Read more

The purpose of this MSc thesis is to do an experimental study into the spatial and temporal variation of rocking armour units. Armour units on a breakwater slope under wave loading can sometimes start to move back and forth, this phenomenon is known as rocking. Rocking can lead to significant impacts between armour units, which can result in breakage. This is especially important for single layer armour units, like the Xbloc. The development of the smart Xbloc makes it possible to measure accelerations and angular velocity with a stand alone sensors at a sampling frequency of around 100 Hz. The current literature does not provide the spatial distribution of the number of impacts and the impact velocities due to rocking. Furthermore, only limited knowledge is available on the distribution in time. The research aim of this thesis is: Determining the spatial and temporal distribution of the number of moving armour units, the number of impacts and the impact velocity of rocking armour units. To achieve this aim a physical scale model was set up and model tests have been performed with 10 smart Xbloc units to measure rocking. The collected data, analysis and results provide a unique look into the behaviour of single layer armour units. The results can be used to validate rocking models and provide valuable statistical information on the number of impacts and the impact velocities.

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