Coastal structures I

While assessing the breakwater stability through a 3D physical model, the normal practice is to modify the structure element if the breakwater is unstable. However, casting a large number of different sizes of concrete armour is time-consuming and costly. This study assessed the utilization of the constructed model with 6.5T(1:41.37) to represent the 10.0T(1:47.82) and 12.5T(1:51.51) tetrapod(TTP) armours by using 88g TTP units in the model. Only the stability of the main armour at the roundhead was considered and the same structure freeboard in the prototype was considered for new scales. Since the measured Hs at the breakwater include wave reflection from the structure wave condition at the paddles was considered while selecting the input signals for the new scales and selected inputs were verified with the post-calibration. Originally proposed 6.5T units were replaced by the hydraulically stable 12.5T units at the roundhead based on the model results.

The coastal structures allow the wave overtopping. However the extreme wave overtopping could cause damages on rear slope. The most of the researches for the armor stability were about on the sea side slope of rubble mound structures. van Gent (2007) performed the experiments about the stability of the rock material on the rear side slope of rubble mound structures with L-shaped crest elements. 
In this study, 2-D model tests were performed to investigate the stability of concrete armor units covered on harbor side slope of rubble mound structures. The rectangular shaped crest elements were applied and the tetrapods were placed on harbor and see side of the rubble mound structures. The stability were investigated using the damage level (Nod=0.5) and it could be known that the armor unit weight ratio for the rear slope of rubble mound structures needed 0.8 times of that for sea side slope. 

The Parsian port, located in southern Iran, features a basin protected by breakwaters that extend to a seabed level of -31 m C.D. In the context of structures situated in deep waters, the toe berm emerges as the optimal choice for breakwater toe layout. Performing experimental investigations utilizing the physical breakwater model become imperative in ensuring the stability of the toe layer in wave breaking affected zone. This paper presents the outcomes of a stability analysis conducted for the Parsian port breakwater in Hydraulic Laboratory at Tarbiat Modares University. Here, various concrete units, including accropodes, cubes, and blocks, were employed to satisfy the stability criteria. The results demonstrate that using concrete units with holes in conjunction with placing a sacrificial rock layer in front of units (main toe layer) is the most effective approach for mitigating destabilizing pressure in comparison to the alternative methods as employing units with higher tonnage.