Study On Bearing Capacity And Performance Of Composite Stone Column In Loess Soil

Loess soil is a kind of light yellow or brownish yellow soil.Its grain composition is mainly silt,with uniform particle size,pores,no bedding,loose and vertical joints.Loess soil is a collapsible soil;thus,it needs to be treated to sustain the superstructures’ load.Loess soil treating methods are many,and Geotechnical engineers are familiar with those methods;one of these methods is to utilize stone columns.Stone columns are one of the ground improvement methods used to increase strength,improve fine-grained soil compressibility,accelerate consolidation,and decrease liquefaction potential.They are mostly used to stabilize deposit soils,including loess soil.Many researchers and engineers have conducted many experiments to evaluate stone columns’ behavior embedded in loess soil.The bearing capacity of stone columns depends primarily on the confining pressure from the surrounding soil.Base-type foundation standing on unreinforced soil(US),ordinary stone column reinforced soil(OSC),and composite stone column reinforced soil(CSC)were used in this investigation.In this thesis,an investigation was performed using the traditional approach of reinforced soil laboratory test and an analytical solution using ABAQUS software.Scaled-down models of an ordinary stone column and a composite-stone column were constructed Separately.The main results of this investigation are mentioned below:1.The composite-stone column shows efficient behavior over the ordinary stone column and the untreated loess soil.The use of the composite-stone column improves the ultimate bearing capacity and decreases soil compressibility.2.The value of lateral deformation of composite-stone columns was reduced by more than half,which indicates the concrete part’s resistance to bulging,and the concrete part transfers the effect of bulging failure to the deeper layers of the soil.3.The concrete part placed at the top of the stone column increased the area’s stiffness in which it was placed.Thus,the composite-stone columns showed a high-stress concentration ratio and high bearing capacity.4.The investigation of horizontal stress demonstrates the method of column failure as well as the critical length of the column,whether it is a long column or a short column.The long concrete part reduced the length of the stone part of the column;thus,the column is subjected to shear failure instead of bulging failure.5.The analytical model illustrated that the concrete part length influences the composite column’s ultimate bearing capacity enhancement.Furthermore,it revealed that the plastic zone generated within the column and started to spread towards the soil.6.The improvement of ordinary stone columns is 12%,and they contribute more than 60%of soil bearing concentration.Composite stone columns have a bearing capacity greater than ordinary stone columns and provide greater reinforcement for loess soil.7.The bulging deformation reached 10 mm in ordinary stone columns.Composite stone columns have greater resistance to bulging deformation;the bulging is small,especially in the CSC15 and CSC20 models.