Thesis (M.Sc.) - Cairo University - Faculty of Engineering - Department of Civil Engineering

This research aims to study soil improvement techniques in soft soil, mainly by using stiffer elements like stone columns or drained elements like sand drains and prefabricated vertical drains (PVDs). At first, modeling techniques were discussed by using Plaxis 3-D and compared with Plaxis 2-D in order to investigate the most probable modeling technique.Then a case study was represented of an embankment constructed upon soft clay stratum in Finland to study the behavior of soft layers under unimproved and improved PVD sections. After modeling verification, which numerical results matched field observations, verified models were used as a parametric study to model stone columns, and sand drains with different diameters in order to compare the rate of consolidation, final settlement, and the relation between axial stiffness ratio with load transfer to split up between stiffer and drainage elements. Finally, design charts have been made to connect the axial stiffness ratio with global safety and settlement improvement factors

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