الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Many studies on the stability of hydraulic structures have been conducted using a two dimensional model, ignoring the effect of the three-dimensional effect of the phenomena which may alter the complete stability of the structure if included in the study. Although uplift force is the most critical parameter for the stability of structures, the seepage and exit gradient also play a role in the stability. Lateral or side seepage changes the phreatic surface around the structure and thereby changes the uplift and exit gradient along the centerline and edges of the structure. The main objective of this study is to investigate in detail the stability of the structure using a three-dimensional model and compare the results to the two-dimensional model. The work intends to analyze seepage discharges underneath and on the side of the structure, exit gradients, and uplift forces. Also, the study focuses on understanding the impact of using a cutoff wall extending in the lateral direction on the seepage parameters. The problem of seepage around hydraulic structures founded on a finite or infinite pervious stratum is carried out numerically by using a computer model, utilizing the finite element method (Midas GTS NX). The software is well documented and validated in the literature and has the options to carry out this work using different boundary conditions. Several configurations of the cutoff wall driven under the structure and extended in the lateral direction are analyzed. The effect of varying the depth of the cutoff wall, the location of the wall, and the length of the wall in the lateral direction are studied both in 2D and 3D, and comparisons between the two cases are outlined. The effect of changing the thickness of the pervious stratum and the use of finite or infinite boundaries are also included in this work. A brief introduction to the topic and a literature review are first presented. Then, the numerical validation of the model is shown by comparing the results of many simulations both in 2D and 3D to analytical, numerical, and experimental results in the literature, and good agreements are obtained. The results reveal that the seepage flow rate has a dramatic difference between the case of the 2D and the 3D due to the flow moving through the surrounding banks of the canal in the latter case. The relative depth of the cutoff wall has a significant influence on reducing the exit gradient in the 2D model. However, in the 3D model, this reduction is not as significant and clear. Increasing the relative thickness of the pervious stratum leads to an increase in the value of 2D seepage quantity and exit gradient as long as the relative thickness is below 2.66 and 2.97, respectively. However, for the 3D analysis, the corresponding values became 2.18 and 2.27, respectively. An increase in the value of uplift force is occurred with increasing the pervious soil stratum thickness if the cutoff wall is in the first half of the structure length, after IX which, a reduction in the value of uplift force is noticed with increasing the pervious soil stratum thickness. Meanwhile, increasing the depth of the cutoff wall and its length in the lateral direction reduces the uplift force even more. By identifying the independent variables, regression models help assess numerical data and get the consequences of the dependent variables (seepage discharge, exit gradient, and uplift force). Contour plots are another useful tool for determining the outcomes of the dependent variables. The Artificial Neural Network, ANN, can describe complex nonlinear interactions and has great fault tolerance, as well as parallel processing that makes it fast and scalable to utilize. The results of the numerical model are compared to the values estimated using the developed relations and contour plots for the dependent variables and an expectable agreement and minimum deviation are obtained. The developed charts and contours will be useful for designing similar structures. A case study is analyzed representing a multiple-stepped weir acting as a spillway weir to get rid of excess water from the West Nubarya Drain and release it to a navigation canal on its downstream side. Different configurations using side drainage along the structure length, lateral drainage, and filter are drawn to increase the factor of safety of the structure against the uplift force. A recommendation is suggested by constructing side drainage as well as lateral drainage with a relative permeability coefficient greater than 4,000 and a small filter width to achieve the best results and minimal cost.