Research On The Stability Of Concrete Armour Units Under Oblique Wave Attack

Rubble-mound breakwater is one of the most common protective structures in coastal and offshore engineering, the role of which is to resist the wave invasion to the coastal zone behind the structure. The history of rubble-mound breakwater can be traced back to the origin of human civilization. Armour units are important structures used to dissipate waves and protect the rubble mound breakwaters and other coastal buildings.In this paper, the development of concrete armour units has been introduced firstly. The artificial concrete armour units have been classified by the number of layers, the control elements to maintain stability on the slope and the feature characters. The advantages and disadvantages of each type armour units have been listed for comparison. The stability, the economies and technical indicators of various armour units have been compared and analyzed in the numerical level.The stability of armour layer against wave action is based primary on the stabilized weight of armour units. The most widely used formulae to determine the stability of armour units, are based on the model testing, which under perpendicular wave attack. But in practical projects, when armour units are attacked by oblique wave, it is usually regarded that the decrease in failure of armour layer compared to normal incidence wave could be ignored. This presume seems to be too careful in calculate the units’stability weight, which is not cost effective. In order to give application guide to calculate the weight of armour units under oblique wave, which guarantees amour layer stability and best benefits in cost,3D model test has been carried out in the State Key Laboratory of Coastal and Offshore Engineering wave basin. Armour layers of Hollow square and ACCROPODETM have been tested, the damage result of the wave at normal and oblique incidence has been analyzed.At the same time, research on the influence of wave steepness and relative depth on the stability of armour units has been carried out. An application guidance is given for the calculation of the units stability weight, which impacted by them.