Shallow mixing and column performances of lime, fly ash and gypsum on the stabilization of swelling soils

Swelling soils are problematic in terms of geotechnics, and they require mitigation actions in preliminary works. The most commonly used method to mitigate the damage caused by swelling soils is to stabilize the soil with chemical additives by using shallow mixing or column techniques. It is important to determine the most suitable additive material and the most appropriate technique when stabilizing swelling soils. The aim of this study is to investigate shallow mixing and column performances of various additives on the stabilization of swelling soils. Lime, fly ash and gypsum were chosen as the additives for this purpose. The study was conducted in the laboratory by creating the model of the land at the laboratory scale. Two different small scale models were designed for each additive, one for investigating their shallow mixing performances, and the other one for their column performances. A curing time of 4 months was considered for all of the models. At the end of the curing time, in order to determine the changes on the swelling behaviour of the soil, free swelling test was carried out on the specimens taken from the small scale model boxes. The results showed that the best improvement was achieved with lime for both techniques with reductions of 99.8% and 51.9% in the swelling percent of the soil when using the shallow mixing and column techniques, respectively. Gypsum, on the other hand, exhibited the lowest performance for both techniques by reducing the swelling percent of the soil by 65.42% with the shallow mixing technique and 25.3% with the column technique. Lastly, the shallow mixing technique showed 47.9%, 64.41% and 40.12% higher performances than the column technique for lime, fly ash and gypsum, respectively.

Automated summary

The study compared the performances of additives in shallow mixing and column techniques by simulating ground models in the laboratory, finding that lime achieved the best improvement for both techniques, while gypsum exhibited the lowest performance. Additionally, the shallow mixing technique showed higher performances than the column technique for lime, fly ash, and gypsum.