J M O Hughes and N J Withers. This paper was first published in GE’s May 1974 edition.
Stone columns, which consist of granular material compacted in long cylindrical holes, are used as a technique for improving the strength and consolidation characteristics of soft clays. This paper briefly describes the history of their use and their empirical design. A series of model experiments were run at Cambridge, using radiographic techniques to determine the actual behaviour of a single column in a uniform normally consolidated clay. Simple results of plasticity theory were used to predict the limiting load. The good agreement between experiment and theory enabled the effectiveness of stone columns, used both singly and in groups, to be discussed.
Stone columns significantly reinforce soft ground. Unlike pile foundations they make very efficient use of the soil near the surface. They are ideal for light loads; however, they are less effective at supporting heavy loads because they cannot transfer the applied stresses to the deeper layers of soil.