الفهرس 
Chapter One: INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The utilization of geotextile has experienced significant growth in coastal and geotechnical applications over the past few decades. For their application fields, specific applications are associated with temporary structures, whereas others are associated with permanent structures. Moreover, their primary objective is to attain increased stability for structures that contain it. The present study primarily focuses on investigating the stability of a marine causeway by suggesting three distinct reinforcement systems. The first proposal system is a geotextile layer reinforcement system (GLRS), which involves incorporating a geotextile layer as several separate layers within the causeway. The second system is a geotextile mats reinforcement system (GMRS). It distinguishes itself from the first system by employing geotextile materials as close mat units to confine the soil within a sealed framework. The third system employed is the geotextile tube reinforcement system (GTRS), which involves the utilization of geotextile tubes positioned within the core of the concerned causeway.
An additional objective of the present study is to gain a more comprehensive understanding of the behavior exhibited by these presented systems across various geotechnical environments. Specifically, the focus will be on three distinct types of soils: dense sand as a main friction soil, silty sand as a friction-cohesion soil, and stiff clay as a primarily cohesive soil.
To accomplish all of the objectives above. A numerical investigation was carried out employing finite element software, ABAQUS V6.14. The numerical investigation was conducted within five separated groups of models, namely the validation models, the reference models, the models incorporating geotextile layers reinforcement system (GLRS), the models studying geotextile mats reinforcement system (GMRS), lastly, the group containing models of geotextile tubes reinforcement system (GTRS).
Two numerical models were created during the validation phase to simulate two small-scale laboratory experiments accurately; one model simulates a geocell-reinforced embankment model ,the other simulates the procedure of filling a geotextile tube. In these studies, numerical results show a good agreement with the experimental results.
The reference models group analyzes the reference scenario of a marine causeway without any geotechnical reinforcement. The loads on the reference models are a surcharge load applied on the crest of the causeway, in addition to the pressure exerted by the surrounding 2.00 m depth seawater. The causeway is 4.00 m in total height and has an angle of 45 degrees for its side slope. The outcomes of the innovative systems will be compared with the results gained from the reference models.
The scope of the investigation was broadened to encompass the parametric analysis phase within the models of proposed systems. This phase involved the examination of multiple parameters that have the potential to impact the performance of a marine causeway. These models constitute the final three groups of models. The results of the parametric study conducted on the (GLRS) indicate that the thickness of the geotextile has the most significant impact on the stability of the causeway. Also, the findings validate that reducing the vertical spacing between layers leads to increased stability.
Furthermore, it is not always necessary for the geotextile layer to reach its maximum length to have a noticeable impact. The influence of the preceding parameter is contingent upon the specific soil type. Based on the obtained results, it can be inferred that the impact of identical parameters exhibits a comparable behavior in the case of the second system, GMRS.
Regarding (GTRS). The impact of filling pressure, unit size, unit numbers, and filling material type has been examined. The findings indicate that zero filling pumping pressure for units in GTRS is recommended to gain higher stability of the marine causeway. On the other hand, increasing the number and diameter of geotube units is essential advice to increase the stability of the causeway. Regarding the studied filling materials, concrete gives the highest stability. At the same time, dense sand soil gives medium stability compared to lower rigidity gained by designing geotubes containing the same type of causeway soil.
Lastly, comparisons between the performance of each suggested system were displayed in the three studied types of soil to have a suitable design for the concerned causeway.