الفهرس 
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Abstract
Stone piles have gained a wide reputation for its credibility as a way of reinforcing soft clay soil deposits through stiffness increase and consolidation acceleration. The current thesis investigates the settlement behavior of two cases of group stone piles in soft clayey soil through finite element analysis using PLAXIS 3D software. Verification of the software was first performed by means of a reported monitored field test and an experimental laboratory study. The first reported case study is a back analysis of a field load test on small group of stone piles located in Port-Said-Egypt. A survey of the soil nature of test site area was performed to investigate the native soil properties in conjunction with the back analysis of a plate loading test implemented on the crushed aggregate stones used in piles construction. For the simulation of actual site properties, sensitivity analyses were conducted to study the stone piles installation effect on native properties changes until reaching the closest model. The enhanced material properties were found to highly affect the settlement results and stiffness behavior, which needs more consideration in numerical modelling and further embedment in design approaches. Afterwards, a parametric study was performed to investigate some of the key parameter effects on the system. The stone piles length (L), stone friction angle (ϕ), and granular mattress thickness placed on top of piles (t) were found to significantly affect the system response. Results of settlement reduction, stiffness improvement, and deformation modes are then presented. The second case study presents the analysis of a proposed design system of large floating stone piles to support a raft foundation in a deep deposit of soft clay. Different key parameters have been studied to investigate the most effective parameters with the results of settlement reduction, system stiffness, and lateral deformation were presented. Finally, the main findings are outlined where the stone pile length was found to affect the system behavior up to a value of about 1.7 to 1.8 B where B is the footing width. The effectiveness of the granular mattress existence was quantified through a new factor that is referred to as “Mattress improvement factor: ηgm”. Results indicate that an average improvement of 65% to 70% can be obtained with the granular mattress presence compared to the zero-thickness case, with a recommended optimum thickness of 1.5 d where d is the stone pile diameter. Further future recommendations are presented at last.