الفهرس 
History of soil mechanicsOnly 14 pages are availabe for public view
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Abstract
Due to a lack of suitable building land, the man was forced to look for weaker ones. These lands’ challenging issues include high settlement, low bearing capacity, and high excess pore water pressure. Scientists proposed various techniques to solve these difficult problems, including dynamic compaction, soil reinforcement, and chemical additives such as cement and fly ash, and pile foundation. One of the most effective solutions that has been used in recent research is the stone column technique. It has successfully supported embankments, bridges, tanks, and buildings. Stone columns are used to reduce settlement and its duration, reduce bending moments on the foundation, and thus reduce foundation reinforcement while increasing soil bearing capacity.
A series of axis-symmetry models using finite element analyses (PLAXIS 3D) were performed to investigate the behavior of a raft foundation over clayey soil improved by stone columns (SC). Clayey soil and stone columns were modelled using hardening soil model, which uses an elastic-plastic hyperbolic stress–strain relation, and the raft foundation was modelled as an elastic element. Several parameters, including number of stone columns (n), length of stone columns (L), Young’s modulus of stone columns (E), thickness of raft foundation (t), and diameter of stone columns (D), are selected in this thesis to investigate the influence of these parameters on the settlement, bearing capacity of soil, flexural behavior, shear of raft foundation, load bearing of stone columns and comparison between stone columns and concrete piles.
Finally, Stone column system is a good method of improving weak soil. the results indicate that by increasing all parametric studies, bearing capacity of soil, load bearing of stone column increased and settlement decreased, while the flexural behavior and shear of the raft foundation decreased in some sections. The most effective parameters for decreasing flexural behavior and settlement are diameter of stone columns (D) and Young’s modulus of stone columns (E); for decreasing shear is (Young’s modulus of stone columns) (E). Concrete pile group is more effective than stone column group in bearing capacity of soil, flexural behavior, shear of the raft foundation and load carried by pile group because Young’s Modulus (E) of concrete pile group is more than stone column group. Finally, comparison between advanced techniques like PLAXIS 3D and ordinary techniques like SAFE software in analyzing the behavior of the raft foundation, which overestimates all results compared with PLAXIS 3D’s values. Some significant observations on the performance of raft-stone column systems with changes in the values of parametric study are presented in this thesis.