Exploration into the mechanisms that govern the stability of an Xbloc+ v1 armour unit
A.B. Vos (TU Delft - Civil Engineering & Geosciences)
S.G.J. Aarninkhof – Mentor
H.J. Verhagen – Mentor
Bas Hofland – Mentor
B Reedijk – Mentor
R. Jacobs – Mentor
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Abstract
In this MSc thesis it is investigated how the first version of concrete armour unit Xbloc+, Xbloc+ v1, acquires its stability. The stability mechanisms are investigated by conducting two type of physical model tests. First, 23 dry pull-out tests are done to obtain insights into the aspects and mechanisms that influence the armour layer stability. At 8 locations per slope, blocks are pulled out to determine the force needed to extract an armour unit. Tests are done on a 3:4 slope with 2 pull-directions; under an angle of 45 degrees with respect to the slope and perpendicular to the slope. Concrete as well as plastic armour units are tested, both having a different surface roughness. The conclusions of the pull-out tests are verified by means of the second type of model tests; small scale physical hydraulic model tests in a 2D wave flume. In total, 10 tests are conducted; 6 tests with plastic armour units and 4 tests with concrete armour units. Each test starts with a run with a small significant wave height which is increased stepwise in each run until failure occurs. All test sections have a 3:4 slope and are subjected to waves with a 4% steepness. Additionally, the influence of the significant wave height step size for successive runs is investigated. The combination of both physical model tests results in recommendations for a change in design which is expected to lead to a higher stability of an armour layer with Xbloc+ armour units.