الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Earth dams are usually built for many purposes, as water storage, irrigation, electricity generation, controlling or preventing flooding, during construction works to divert the river flow, etc.. In Sinai, Egypt there are many small earth dams’ projects are built to be used as a barrier to protect the governorate from heavy rains. Earth dam failure is considered a major issue because it causes significant economic and environmental damage. Earth dam failure can occur for variety of reasons, however historical dam failures statistics revealed that overtopping is the most common cause of dam failure. As a result, several researchers attempted to understand this failure mechanism and the elements that influence this type of failure. In this study, different parameters are experimentally investigated to determine their influence on the failure of non-cohesive earth dam due to overtopping. Influence of tailwater depth, using different percentages of silt in the dam mixture, changing downstream slope configuration by cutting a berm with varying widths and heights, lining position, and slope of downstream fill are investigated. The main purpose of this study is to increase the total time of failure and reduce the peak discharge to provide the region downstream of the dam with sufficient time to evacuate. For each experiment, the development of dam profile, the total time of failure, the peak discharge and its time are all recorded and analyzed. The results showed that increasing the tailwater depth reduces the erosion rate, the eroded volume, and peak discharge. Also, within the range of the tests parameter it is recommended to use silt in the dam soil mixture with a percentage not less than 16%. Cutting a berm with relative berm width = 0.33 and relative height = 0.67 increases the total time of failure, reduces the peak discharge and increases its time. Lining the upper part of downstream slope and crest width significantly increases the total time of failure by four times than the case without lining and delays the occurrence of peak discharge up to 95% of the total time of failure. Using a downstream fill (50% silt and 50% rock) with slope 4:1 and relative height = 0.5 is recommended to reduce the peak discharge and increase the total time of failure.In addition, an evaluation of Flow 3D numerical model in reproducing the erosion process is performed. The experiment of the dam with relative berm width = 0.33 and relative height = 0.5 is chosen to be simulated by the numerical model. A comparison between experimental and numerical models results for total time of failure, peak discharge and its time is obtained, and the percentage of error is calculated. Also, the effect of Angle of repose and Entrainment coefficient is investigated. It’s found that Flow 3D model can successfully replicate the erosion process of non-cohesive earth dam failure. However, it is noticed that the model overestimates the peak discharge for all cases of angle of repose while underestimates its time. A case study is chosen to be simulated with Flow 3D to determine the influence of crest width and the position of discharge channel on the failure mechanism. The case study and numerical model results are compared, and the percentage of error is computed and found. It is concluded that Flow 3D is a sufficient tool for reasonable estimation of the total time of failure and peak discharge during non-cohesive earth dam failure by overtopping.