Investigating the effect of sample disturbance, compaction and stabilization on the collapse index of soils

Collapsible soils are problematic soils, which support heavy loads at their natural water content, but as their water content increases, they undergo a considerable reduction in volume. This research presents results of single oedometer tests for determining the collapse index of undisturbed and remolded soil samples. The alteration in this index was investigated by applying disturbance to samples. Samples were remolded by different dry unit weights and water contents. Additionally, some samples were stabilized with cement kiln dust, lime, ammonium sulfate and potassium chloride to investigate their effect on the collapse index. The results indicated a greater collapse index for undisturbed samples compared to that of remolded ones. It was also found that increasing water content and dry unit weight contribute to collapsibility reduction and stabilization, making it possible to minimize the collapse index to the degree of non-collapsible soil. Reduction procedure is affected by amount of additives, dry unit weight and water content of samples. In addition, curing time of samples was another effective factor for cement kiln dust and lime.