The Experimental and Numerical Studies of Encased Stone Column Individually, in Group and Nucleated on Improvement of Loose Sandy Soil

The stone columns, as a method of soil improvement, significantly reduce soil settlement due to incoming loads and increase soil load-bearing capacity. Adding geotextile as a stone column encasement has a considerable impact on this relationship. In this study, the amount of loose sandy soil settlement was investigated by numerical modelling of stone columns with the Plaxis 3D Foundation software, and the results were validated by using laboratory modelling,. For this purpose, a single stone column was modelled in two modes of rainfall density and compacted states and continuously the group mode in the soil was investigated. Also, the effect of adding geotextile encasement to the inner part of stone column investigated as a central core. So, a 6 centimetre diameter of central core that surrounded with geotextile encasement has considered inside of a 10 centimetre diameter of stone column in both rainfall density and compacted state. The results of experimental and numerical modelling were well-matched with each other. Also, it was clear that the increasing of stone column number and compaction can enhance soil bearing capacity, considerably. The adding of central core has had considerable effect on soil bearing capacity, too. This is due to the increase of all-round stress in the interior of the stone columns. The results showed that the stone column with a diameter of 10 cm increased the bearing capacity compared to unreinforced soil by 36%, while in the stone column with central core in rainfall density and compacted states, this amount is 43% and 54%, respectively. Also by evaluation of appearance deformations in stone columns after loading showed that increasing the density and adding geotextile encasement to the central core has a considerable effect on the created deformations and prevention of local ruptures and the process of deformation becomes more favorable.