Briefing: Compacted soil columns for collapsible lateritic soil improvement

Large areas of Southern Brazil are covered by thick layers of colluvial soils that have been affected by the laterisation process; this is typical of tropical regions. In their natural unsaturated condition, these soils, with porosities of ∼50%, can experience large and sudden volume reductions upon wetting and are generally identified as collapsible soils. In contrast to this behaviour, when compacted, these soils exhibit good mechanical properties and are used as construction material in the base courses of roads, as well as in some major Brazilian dams and embankments. Compacted layers of these lateritic soils have also been successfully utilised to allow the use of shallow foundations in collapsible soils. An adaptation of this technique was evaluated in this study – that is, the use of compacted lateritic soil columns to improve collapsible soil performance. The efficacy of the method was verified by plate load tests carried out on collapsible lateritic soil, with and without a compacted soil column, at the University of São Paulo in São Carlos City, Brazil. The preliminary results encourage the authors to continue this research in order to confirm the findings and to define guidelines for the practical use of this method.