Behaviour of Encased Floating Stone Columns

Abstract

In this paper, the finite element method is utilized as a tool for carrying out differentanalyses of stone column–soil systems under different conditions. A trial is made toimprove the behaviour of stone column by encasing the stone column by geogrid asreinforcement material .The program CRISP2D is used in the analysis of problems. The program adopts thefinite element method and allows prediction to be made of soil deformations consideringMohr–Coulomb failure criterion for elastic-plastic soil behaviour.A parametric study is carried out to investigate the behaviour of ordinary andencased floating stone columns in different conditions. Different parameters were studied toshow their effect on the bearing improvement and settlement reduction of the stone column.These include the length to diameter ratio (L/d), shear strength of the surrounding soil and,the area replacement ratio (as) and others.It was found that the important increase in strength of stone column occurs when itis encased by geogrid for (length/diameter) L/d = 8 while in case of L/d = 4, a slightincrease in the bearing improvement ratio at the early stages of applying the load isobtained and then the value of (q/Cu) for both ordinary and encased stone columns is thesame.