Stone columns are often considered as an excellent ground improvement technique adopted to improve the load carrying capacity and reduces the settlement characteristics. However the load carrying capacity mainly depends on the undrained shear strength of surrounding soils. Reinforcement in the form of encasement is usually provided around the stone columns which imparts lateral confinement, resulted in improved load carrying capacity. This geosynthetic encasement also acts as an excellent filter, prevents the entry of finer clay particles and offers better drainage path for pore water dissipation. Vacuum consolidation is a type of preconsolidation technique in which applied vacuum creates negative pore pressure which increases the effective stress without altering the total stresses. The improvement in effective stress thus leads to increase in undrained shear strength of clay soils. The research work involves application of vacuum through encased stone columns and tests done to study the improvement in load carrying capacity of encased stone column after vacuum application. Soil samples after the vacuum consolidation were also taken to study the increase in undrained shear strength after vacuum application.
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