The behaviour of stone columns has yet to be captured fully by analytical and numerical techniques, and predicting column behaviour in soft cohesive soils brings specific challenges. This paper provides a comprehensive review and assessment of some aspects of field performance of stone columns in soft clays and silts, from both published and unpublished data and for loading over both wide areas (i.e. embankments) and small areas (i.e. footings). In particular, a new database of settlement improvement factors is developed, which gives an indication of the reliability of a traditional analytical approach, as well as distinguishing clearly between the performance of the preferred dry bottom feed system and other column construction systems. The paper gives evidence highlighting the key construction issues central to the successful performance of treated ground. Some data are also presented on pore pressure and total stress changes as a result of column installation and loading, and interpretation of these data benefits from a direct comparison with driven piles.

Measurements of ground heave induced by installing stone columns in soft clay are presented in this paper. These measurements are likely to provide guidance to practitioners concerned about the possible impact of column construction on adjacent structures and services. Heaved volume, variation in heave with radius and the radial extent of heave were found to follow experience of driven piles. Simplified finite-element analyses have also been performed which indicate that the thin stiff crust typical of soft clay profiles appears to have little influence on heave, whereas soil stiffness variation with depth and column length may be influential.

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