Behaviour of Encased Stone Columns in Soft Clay

Abstract

Ground improvement techniques are commonly used in different construction sites where the existing soil conditions are very weak and can lead to unsatisfactory performance. Encased stone columns technique is employed to enhance the bearing capacity, shear strength, and stiffness of soil to reduce settlement, and accelerate the consolidation rate of soft soil. In this research, a series of (62) cases have been studied to investigate the behaviour of a single encased stone column in soft clay to figure out the encasement effect and its properties compared to that without encasement using a finite element model (FEM). PLAXIS 3D software package was used in this study stone columns with two diameters (D=0.4m and 0.6m) and the length of the stone column to the diameter (L/D) ratio is kept equal (10) in all cases. Two cases of stone columns were studied: without encasement which is an ordinary stone column (OSC) and with encasement as encased stone column (ESC) column which is surrounded by geotextile with different stiffness. At an internal friction angle of the stone column =45°, the increase in the BCR of the encased stone column over the case of untreated soil was found to be 227% and 200% for the two cases of column diameters (D=0.4m and 0.6m) respectively.