6 - Stone column method

Abstract

Stone column method for ground improvement is a vibro-replacement technique where the weak soil is displaced using a cylindrical vibrating probe (i.e. vibroflot), thus creating a column that is then filled and compacted with good-quality stone aggregates. With the inclusion of stone aggregates to the in situ soil, its stiffness and load-carrying capacity increases. It also helps to reduce the static as well as differential settlement of the soils. Bulging action of the stone columns imparts lateral confinement to the surrounding soils and it also acts as a drainage path accelerating the consolidation of cohesive soils. These stone columns are generally used for soils that are much more compressible but not weak enough to necessitate a pile foundation. Moreover, for the construction of low-to-medium rise buildings on soft soils, pile foundation sometimes becomes expensive. In such cases, stone columns are preferred. Stone columns are very useful for the improvement of cohesive soils, marine/alluvial clays, and liquefiable soils. Stone columns have been used successfully for a wide range of applications from the construction of high-rise buildings to oil tank foundations, and for embankment and slope stabilization. In this chapter, the mechanism of ground improvement using stone columns, the installation methods of stone columns, and the various design parameters for construction of stone columns are presented.