الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Nowadays the problem of negative skin friction (NSF) is mostly popular due to the improvement of methods of foundations. Piles are widely used because it can carry large loads, easy to implement and its ability to transport the loads to strong soil layers. In case of using pile foundations in consolidating soil the soil may settle more than piles which produce (NSF) and loads in piles which may not calculated in the design and might cause structural failures. This condition can occur by lowering of water level in compressible soils and by increasing in the effective stresses by surcharge loads. NSF induces an additional compression force on the pile called drag-load as well as an extra pile displacement called down-drag. The mechanism of (NSF) on pile is still not well understood and often several pile design codes provides different recommendations to calculate (NSF). In this research (ABQUAS 6.14) program used to study the behavior of single induvial pile, 4-pile group and 9-pile group in consolidating soil. Different parameters were studied such as different axial loads, surcharge load, post consolidating load, lowering of water table, different tip conditions, different cap thickness, the effect of change in slope of critical state line (m), the effect of consolidation parameters λ and k and the effect of change in pile modulus of elasticity. During the analysis, negative and positive skin friction, accumulative shaft load, drag-load, down-drag, soil settlement, excess pore water pressure and estimated 𝜷 are obtained at different degrees of consolidation. The results revealed that; drag-load and down-drag are time dependent. As the axial pile head load increased the peak drag-load decreased in both cases single individual pile and pile groups. The surcharge load affected on the soil settlement and excess pore water pressure. The simultaneous loading and post consolidation load have the same effect on drag-load and negative skin friction.