الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The essentiality of upgrading new coastal structures to withstand the increasing storms violence due to climate change and to be environmentally friendly coastal protection techniques are contemporary matters to be addressed in the present study. In addition, the growth in the marine sector prompts a significant need to construct new types of economically and environment friendly coastal structures. One of the most widely used coastal structures is the conventional seawall that are used to protect coastal areas from wave-induced erosion. As well as the massive breakwater that is used to form a sheltered area for harbors purposes. Through this study, two innovative types of coastal structures are discussed. These two types have been investigated deeply in the wide wave flume of Coastal Research Institute (CoRI). The first structure is Perforated Quarter Circle Seawall (PQCS) that developed to introduce a seawall with high efficiency to absorb high incident wave energy resulted from storms violence due to climate change. Furthermore, it consumes low concrete that will decrease CO2 emission from concrete. The proposed seawall has many merits such as a light weight, requires less materials, suited for poor soil conditions, easy to construct and remove, aesthetically acceptable, cost effective, eco-friendly and stable. The proposed seawall was investigated physically in the wide wave flume under the effect of regular waves. To investigate the effectiveness of PQCS in terms of wave reflection coefficient (Kr), wave dissipation coefficient (Kd), and wave overtopping, 288 experiments were conducted. Three seawalls with different perforations ratio have been investigated: 42%, 21% perforations and a solid case. Furthermore, for each perforation ratio, five alternative modifications were performed to test their influence on the efficiency of the structure, including an extended rear wall, a parapet rather than the rear wall, a parapet above the rear wall, a sidewalk and a sidewalk with a parapet above the rear wall. In addition, each alteration was tested in three different water depths, each depth case was subjected to six different waves conditions (different wave height and wave period). Regarding the wave reflection and dissipation efficiency, it is found that the perforation ratio has a significant impact on structures efficiency, by increasing the perforation ratio the structure’s efficiency increases. The partially submerged structure shows the best efficiency, the high perforation model shows a reflection coefficient range from 0.08 to 0.5, while the dissipation shows values ranging from 0.88 to 0.98. The medium perforation shows a reflection coefficient ranging from 0.27 to 0.54, while the dissipation shows values ranging from 0.86 to 0.96. The solid model shows reflection coefficient values ranging from 0.49 to 0.83. While the wave dissipation coefficient shows values ranging from 0.56 to 0.86. Regarding the wave overtopping, it is noticed that, the wave overtopping decreases significantly with increasing perforations ratio. The mean wave overtopping is drawn alongside with the tolerable wave overtopping for people and vehicles. It is found that the best modification that introduces a tolerable overtopping rate for people (below 1 Liter/Sec/m) is the recurved parapet and up-rush zone especially for the high perforation case. This case introduces a dimensionless overtopping (√𝑔𝑞𝐻3) values range from zero to 0.005. The other innovative structure is hollow artificial shell shape blocks. This type of shells is distinguished among other species. Its length and width are almost twice the height which increases the stability of every individual shell. The out-layer grooves and the semicircular shape smoothly dissipates incident waves. This new type will help to achieve a specific prominence in developing sustainable coastal management strategies and widely recognized as cost-effective, ecofriendly, esthetic, and multifunctional coastal structures especially for recreational coastal areas. Three cases of submergence for the two and three staggered shells rows that based on a rubble foundation have been checked. Furthermore, a number of perforations have been added to the shells to release the gathered air internal the shells that can V affect the structure stability. The efficiency of the proposed breakwater has been introduced in terms of wave reflection coefficient (Kr), wave transmission coefficient (Kt) and wave dissipation coefficient (Kd). The two and three shell rows for partially submerged case show the better efficiency has been compared with some of the other breakwater types. The summary of results revealed that the partially submerged case shows the best efficiency compared with other conditions whether the two or three shell rows. In case of two rows, Kr shows values ranging from 0.11 to 0.37, Kt shows values ranging from 0.3 to 0.45, and Kd shows values ranging from 0.82 to 0.95. The case of three shell rows shows efficiency values more than the two perforated shell rows. Adding the third row can show reflection values 1.8% lower than the case of two rows, while the wave dissipation coefficient can show 2.5% lower. The main effect is on the wave transmission which decreased the transmission coefficient 8.8 % lower than the two rows of shells. The partially submerged case is compared with other breakwater types. The efficiency of the proposed structure is comparable with the breakwater with different types of armor layer with slightly improvement. Using the artificial shell block over the submerged breakwater crest can reduce the crest width to 20 to 30% of its design width with the same efficiency. In addition, perforated shells blocks can be used to enhance the sea life environment.