Comparative settlement response of soft clays reinforced with granular columns under widespread loads

This paper examines the consolidation and settlement behaviour of soft clay deposits treated with granular columns (single and in groups). Two Rowe cell loading chambers were used to conduct the investigations on samples of kaolin and a local Belfast natural estuarine alluvium called ‘sleech’. Tests were carried out on unreinforced samples and then reinforced samples with single and multiple column configurations. The test duration for each test was between 3 and 4 months, depending on the test material and the granular column configuration. The settlement reduction factors based on primary and secondary consolidation were examined. The study suggests that the effectiveness of granular columns at mitigating primary and/or secondary settlement is directly related to the loading intensity, the stress history and the creep characteristics of the subsoil. It was also found that the stress concentration ratio reduced with the stress level. Secondary consolidation also has some effects on the stress concentration ratio.