الفهرس 
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Abstract
Recently, because of the significant growth in construction of high-rises buildings, offshore ports, wind power mills, storage silos and many other types of heavy loaded structures, large diameter bored piles are attributed to be the most powerful element of deep foundations that can successfully be utilized in different subsurface conditions. The in-situ full scale pile loading test is the most recommended methodology in several international geotechnical codes and foundation design standards to determine the ultimate capacity of large diameter bored piles in spite of its high cost as well as time consumption; However, loading these piles till reaching apparent failure is hard to achieve especially for working pile. Implementation of these piles perform a large part of the project total cost. So, it was necessary to find new methods that reduce the project’s total cost such as finite element analysis (FEM) that simulate the behaviour of large diameter bored piles. In recent years, the acceptance of Finite Element calculation and Numerical Analyses are rising more and more in geotechnical problems used in foundation designs, because of the rapid development of the domestic economy and increase the proportion of investment in infrastructure projects. In this study, large diameter bored piles were used in two of the most important projects in Egypt, the first one is a new container terminal at east Port Said port, this project comprises the construction of approximately 2.5 KM of new quay wall fully equipped to accommodate large container vessels. The second one is in the New Administrative Capital of Central Business District (CBD) project that located at a distance of about 45 km east of Cairo. Behaviour of load-displacement curve of large diameter bored piles varies from region to another according to the soil strata, these curves can be calculated by using the results of in-situ pile loading tests. Numerical approaches are amongst the promising tools that can be adopted to assess the bearing capacity of piles. The aim of this work is to study theoretically load-displacement behaviour of large diameterbored piles at different locations in Egypt, based on fully-scale pile load test results. As well as, using numerical analyses to simulate load test of a large diameter bored pile performed in multi layered soil under loading cycle at the study areas and determination the settlement of piles. Then comparing the results and also, clarifying the compatibly between the two methods. PLAXIS-2D, V 8.2 program was used in this analysis with different types of models to simulate the piles and the surrounding soil. The objective of this research is compared numerical analysis using PLAXIS with field loading test measurements both in loading and unloading cycles also, in the prediction of the ultimate loads. As well as the effect of dilatancy angle on pile load transfer mechanism was investigated. Due to the very good agreement between field loading tests and numerical analysis, PLAXIS was used to appreciate a reduction in the pile parameters either diameter or length with the well calibrated numerical models were used to study the effect of changed in the pile parameters. Then, recalculating the ultimate capacity of piles and also, the factor of safety. Consequently, the construction’s cost of piles will be reduced to 40% - 50% out of the total actual cost as a result of changing the length, but this ratio has changed to 20% - 30% due to the change of diameter. In conclusion, PLAXIS can be a substitute for in-situ loading tests in the study areas, whether in the calculation of bearing capacity, settlement or change the pile parameters thereby reducing the total cost of the project and the saved money is invested in establishing more infrastructure projects and increasing the national income.