الفهرس 
Abstractيوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
Usage of pile foundation became one of the most popular solutions to overcome the problems which take place due to the presence of heavy structure loads and the weakness of soil resistance to sustain those loads.One of the problems that may encounter during design and construction of pile foundation is the presence of piles in compressible soils. Presence of loading conditions on ground surface and pile head cause settlement of the soil surrounding the pile and downward movement to the pile. This relative movement is the mean reason for the generation of skin friction along the pile shaft. This skin friction may have positive or negative sign. If the settlement of the pile has a larger value than soil settlement, this means that the sign of resulted skin friction will be positive and is called positive skin friction (PSF). On the other hand, if the value of soil settlement is larger than the pile settlement, the resulted relative movement will be negative and skin friction in that case will be negative (NSF). Presence of NSF or downdrag causes an additional load on the pile, this load is called dragload. OBJECTIVES OF STUDY: The main research objectives are investigating the effect of different factors on piles subjected to negative skin friction. Studying the effect of the soil surrounding the pile, pile characteristics, pile-soil interface properties, loading conditions and model dimensions on the values of negative skin friction. Discussing in details the effect of these previous factors on the location of neutral plane (NP). STUDY PROCEDURES: In present study, Numerical model using Abaqus\CAE V6.10 is used to investigate different factors that may affect negative skin friction on piles. This program uses nonlinear finite element method in solving problems. Two dimensional )2D) and three dimensional (3D) models for pile constructed in surrounding soft consolidating soil and pile tip is rested on bearing layer. Consolidating soil surroundingthe pile is assumed to adopt Modified Cam-Clay model, while bearing layer is modeledusing Mohr Coulomb Model. And the behavior of pile material is assumed to be isotropic linearly elastic behavior. Conclusions: Study results show that the value of dragload and downdrag of the pileincrease with increasing the values of used soil properties, hydraulic conductivity, the ratio between consolidation layer and bearing layer modulus of elasticity, consolidation time and the value of surcharge load applied on ground surface. Neutral plane (NP) depth influenced greatly due to using bitumen coating on pile shaft, the value of pile-soil interface friction coefficient, type of used pile(friction or end-bearing) and pile head loading.