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SUMMARY, CONCLUOSIONS ANDRECOMMENDATIONS8-1 Summary:In this study, the efficiency of three breakwater types was studied theoretically and experimentally, for determining the most efficient and economic breakwater characteristics. The first breakwater model consisted of a caisson partially immersed in the seawater and supported on a large spaced pile system, while the second breakwater model consisted of closely spaced vertical square or circular piles and the piles were arranged in one or two rows. The third breakwater model consisted of a caisson, this caisson is partially immersed in the seawater and supported on a closely spaced pile system. Such structures can be used for coasts or small harbors protection.In this thesis, two theoretical studies were presented to estimate the efficiency of the caisson supported on a large spaced pile system and pile breakwaters consisted of one row of circular and square piles. A computationally efficient method, an Eigenfunction method, is used in predicting the efficiency of these types of breakwaters as a function of transmission and reflection coefficients.Experimental study was carried out to investigate the efficiency of the caisson supported on a large spaced pile system and pile breakwaters consisted of one row of circular and square piles to check the validity of the proposed two theoretical models. In addition the caisson supported on a closely spaced pile system and pile breakwaters consisted of two rows of circular and square piles arranged in straight and staggered positions were also studied. Additionally, the effect of the three breakwater types on the scour at the breakwater zone was investigated to determine the maximum scour and deposition.A complete design for two application examples of the studied breakwater models using the available environmental data was made for two Egyptian coasts. This is for estimating the total breakwater cost for each area and comparing these costs with the typical breakwater types. The first model used for Hurghada coast at the Red sea for marina protection and it consists of a reinforced concrete caisson supported on a closely spaced pile system. The second model used for Sidi Kerir coast at the Mediterranean sea for shore protection and it consists of one row of a closely spaced circular piles.8-2 Conclusions:The relevant conclusions of the studied breakwaters can be presented as follows:8-2-1 Caisson Breakwaters on Piles:1. The breakwater is efficient in controlling the transmitted waves when the relative breakwater draft (D/h) is greater than 0.4 and the beach slope is nearly flat. This breakwater efficiency ranges between 60 and 80% in damping the incident wave energy.2. This breakwater type is effective in damping waves when the breakwater width (B) is equal to the water depth (h), i.e. B / h = 1, after which this type of breakwater become not economically effective.3. For short waves, the breakwater is very effective in reducing the incident wave energy, regardless of the structural arrangements and seabed conditions.4. Decreasing the gap between the supporting piles of the breakwater along with increasing the pile diameter resulted in enhancing the efficiency of the breakwater by about 5 to 20%, as obtained from the experimental results. However, when the waves become closer to the short type, this effect is not significant.5. The maximum scour around the supporting pile system (Dsmax) ranged between 0.10 and 0.12 from the water depth, as the dimensionless wave number (kh) ranged between 0.26 and 0.62. On the other hand, the maximum deposition shoreward the breakwater (Ddmax) ranged between 0.05 and 0.10 from the water depth, for the same dimensionless wave number (kh).6. The proposed theoretical model showed good estimation for the breakwater efficiency as waves become short (kh 1.04). In addition, the present theoretical model overestimates the breakwater efficiency by about 5 to 10% as waves become long (kh < 1.04).8-2-2 Pile Breakwaters:1. This type of breakwater is highly effective in damping the incident wave energy for short waves especially when the gap-width or diameter ratio (G/d) decreases. The range of this factor lies between 15 and 30%, according to the experimental results.2. The efficiency of the double row models is more than that of the single row model by about 20 to 30%, raising questions about the economic validity of the double row condition. Moreover, increasing the relative distance between the two pile rows resulted in only about 10% increase in the breakwater efficiency.3. The pile arrangement has a slight effect in the efficiency of the breakwaters, with the staggered arrangement more efficient by only about 5% over the linear arrangement.4. The square pile breakwater is more efficient than the circular pile breakwater by 20 to 25 %.5. The maximum scour around the piles (Dsmax.) ranged between 0.2 and 0.3 of the water depth as the dimensionless wave number (kh) ranged between 0.46 and 1.51. On the other hand, the maximum deposition shoreward the breakwater (Ddmax.) ranged between 0.1 and 0.15 from the water depth as the dimensionless wave number (kh) range between 0.26 and 0.8.6. A reasonable agreement is obtained between the theoretical and the experimental results. In addition, a reasonable agreement is also obtained between the theoretical and experimental results presented by other authors.8-3 Recommendations:The following recommendations are suggested for further studies:1. Developing a numerical model for analyzing the combined effect of the caisson and supporting pile system on the wave attenuation.2. Studying the efficiency of the proposed breakwaters when subjected to oblique incident waves.3. Studying the efficiency of the proposed breakwaters under current-wave system.4. Studying the efficiency of the proposed breakwaters under the action of the irregular waves and wave spectra.
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