The difference between theory and practice in the performance of stone columns in very soft clays.

What is it about?

Field studies have shown that the settlement reduction achieved by stone columns in very soft clays falls increasingly short of theoretical predictions as the distance between columns decreases. The discussion paper describes how ground displacement during column installation is the probable cause of this shortfall in practical performance. It is also suggested that the method of procurement has contributed to reported serviceability failures of stone columns supporting floor slabs on very soft clays. The paper critically discusses the lack of research and development with respect to stone columns and how the method of procurement can influence the level of technical input to the design and construction of the columns.

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Why is it important?

The paper and the discussion present, for the first time, the effect of installation disturbance on the settlement reduction achieved by stone columns in very soft clay. The paper and discussion also present a critical appraisal of how the most commonly used method of procurement for stone columns i.e. design and build, can lead to inadequate geotechnical engineering input. The discussion also raises the issues of lack of research and development with respect to stone columns in very soft clays and excessive risk taking by inexperienced practitioners.