الفهرس 
Chapter (1) IntroductionOnly 14 pages are availabe for public view
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Abstract
A common approach for ground improvement of soft soils is installing stone columns to increase the bearing capacity, reduce the settlement, and accelerate the consolidation time. However, stone columns may not have sufficient capacity in very soft formations due to the lack of confinement of the enfolding soft soils
The intrusion of soft clay into the column aggregate also hinders the effective drainage function of the columns. An ideal solution for the above-mentioned shortcomings is to include geosynthetic encasements around columns. The encased stone columns have been recently increasingly used in place of the uncased columns. However, the available geotechnical literature covering this relatively recent improvement technique is still not fully mature to completely assimilate the varied factors influencing this technique. This study uses a three-dimensional finite element analysis to evaluate this technique’s performance and parameters for different column configurations and geotechnical conditions. A published well-instrumented case study for a test embankment is utilized to validate the model for the parametric analyses. The extensive measured data, including vertical and horizontal deformations, excess pore water pressure, and geosynthetic tensile stresses, are used in the validation process. The model was also adjusted to match an established analytical method that covers specific limited cases; the model results partially agreed with the analytical solution. A parametric study is conducted to address the impacts of the different influential factors, including the column diameter, the stones’ modulus of elasticity and friction angle, the geosynthetic encasement length and ring tensile modulus, and the working platform thickness. It was concluded that by increasing the diameter, modulus of elasticity, friction angle, geosynthetic length, and geosynthetic ring tensile modulus, the settlement under the embankment nonlinearly decreases, and the time needed to reach the final settlement decreases with different influences of each parameter. The results are presented in graphs to allow the geotechnical practitioner to best exploit this technique by optimizing the configuration and the parameters of the encased columns using the presented results.