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A NEW RESEARCH REVEALS THE STABILITY OF DOUBLE LAYER ARMOR BREAKWATER

 

Breakwater is an important component in port development and planning. It also protects the area in the lee side and inside the port from wave attack. Such do produce a force on the breakwaters due to wave breaking, reflection, refraction and resulting rip currents.

Normally, majority of the conventional and low crested structures are composed of armor layers of different units, bedding layer of different smaller materials and toe protection consisting of armor layer units or smaller.

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The resulting forces on the structure affects the stability of the breakwater armor layer including the armor, toe and rear side of the breakwater.Designed breakwater should be modeled and tested to validate its functional design and to check the structure stability under the effect of the wave attack.

Physical models are very useful tool to gain improved understanding of existing physical structures and processes which are currently felt to be too complex to be addressed with analytical or numerical models, and 3D larger scale structural models are commonly used for stability models.

A research has been carried out to investigate the armor layer stability of the new breakwater of EI Dikheila Port. According to the research journal released at sciencedirect’s website featuring; Abdelazim Mohamed Ali, an associate professor at the hydraulics research Institute (HRI), National Water Research Center (NWRC), Delta Barrage, Egypt since 1989. And Al Sayed Diwedar, a researcher for the Hydraulics Research Institute (HRI) since 2002.

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In the research, an undistorted physical hydraulic model with a scale of 1:39:73 was employed as a tool to simulate the existing and the proposed new breakwaters. The physical model was constructed in the wave basin of the HRI.

The armor layer of the new breakwater was tested with regular and random placement for the trunk and the roundhead. The model results showed that regular placing exhibited higher stability for initial damage and gradual damage progression than the random placement of the armor units.

In the research problem, one of the main elements in the port planning is the breakwaters which are used as a protection measure against wave attack and to create safe conditions for mooring from high wave agitation inside the port, especially the northeast.

The existing breakwater protects EI Dikheila port from waves coming from northeast only and falls to protect the port from northeast waves. Therefore, a new breakwater is proposed to protect the port from waves blowing from northeast.

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With the aim of solving the existing problem of wave attack from the northeast and wave agitation inside the port, the research seems to record a great success. The proposed breakwater design needs to be tested for stability before its construction, since the main objective of the research was to investigate the stability of the armor layer of the new breakwater.

The stability investigation includes the stability of the head and adjacent trunk sections. And the stability of the proposed breakwater armor layer units with the regular and random placement.

One of the method employed in the research was an undistorted fixed bed with 1:39:73 physical scale model which was designed to test the stability of the armor layer of the trunk and the roundhead of the new breakwater of EI Dikheila Port and to study the wave conditions around the breakwater and inside the port.

The result of the research was obtained by recording the damage of the armor layer for each test run and the percentage damage was then calculated based on the number of cubes that moved or rocked in place. For the bedding and the toe layers, the percentage of damage was estimated due to the difficulties of defining the number of stones that moved from its place.

The damage obtained was defined based on the CEM {17} as Nd i.e. the number of displaced units/total number of units in referenced area. The displaced units are defined as the units that moved more than its Dn. The breakwater was exposed to different wave conditions simulating calm, design and storm conditions, two cases of armor layer placing were investigated, and in all cases the regular placement was found to be more stable.

The result also showed that in the case of increasing the water level, the damage level increases with the two types of unit’s placement.

 

 

 

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Originally posted 2018-09-27 09:34:58.

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