Investigative Modelling of Behaviour of Expansive Soils Improved using Soil Mixing Technique

This paper presents an investigative modelling of the behaviour of expansive soils improved using the soil mixing technique. In this study, the effect of cement and the inclusion of cementitious by – product materials such as Pulverised Fuel Ash (PFA) and Ground Granulated Blast Furnace Slag (GGBS) was investigated on the swelling behaviour of expansive soils through laboratory analysis and numerical modelling. Laboratory tests to determine the index properties of the natural soils and the improved samples were performed in accordance to current British Standards. Recent study [1] have shown that soil/cement/binder mixes modifies the plasticity properties of the mixed product at a water – to – cement ratio of 1:1. In this study, the analysis of the swelling behaviour was carried out using existing Plasticity Index (PI) - based correlations and one – dimensional oedometer test. Complimentary numerical modelling using MIDAS program was also performed. The analysis of result indicated a reduction in the plasticity index of the treated samples compared to the initial values of the untreated expansive soils. By using the PI-based equations, the swelling potential of the treated soils were effectively quantified and compared with the laboratory and numerical studies to determine the degree of variations from those of the untreated soils. Both experimental and numerical model showed a reduction of swelling potential of the treated expansive soil in the range of 43 – 80%.