Expansive soils undergo swelling and shrinkage due to seasonal moisture fluctuations and cause severe damage to the lightly loaded structures constructed on them. To avoid these damages, these soils are commonly stabilized with techniques like Cohesive Non-Swelling Soil (CNS) technique, ponding and lime stabilization by physical mixing for shallow depths and Lime Piles (LP), Lime Columns (LC) and Lime Slurry Pressure Injection (LSPI) techniques for expansive soil extending to greater depths. In view of the implementation difficulties and limitations of LP, LC and LSPI techniques in stabilizing the expansive soils, recently, a new method – Lime Precipitation Technique (LPT) – was proposed in the literature. However, the studies on LPT were limited to the laboratory scale investigations using LR grade CaCl2 and NaOH and the effectiveness of LPT technique in stabilizing the expansive soils in the field is not evaluated. Further, all the field studies using different stabilization techniques were carried out in summer season only. Therefore, there is a definite need to understand the relative efficiency of commercially available CaCl2 and NaOH solutions, individually and combined for LPT, and lime for LS in stabilizing the in-situ expansive soils at both shallow and deep depths.

To achieve this objective, first a comparative laboratory study was carried out using CaCl2 and NaOH solutions both individually and combined for LPT stabilization and LS stabilization for understanding the mechanisms and optimum dosages. Then, for the field study, four boreholes of100 mm diameter (d) and 1.20 m depth were made using a hand auger in the selected test area at NIT Warangal campus and the required quantities of desired solutions were poured into the boreholes for deep stabilization. In case of shallow stabilization, four test pits of size 1.2 m × 1.2 m × 0.3 m were excavated for ponding. The in-situ heave of the expansive soil due to the permeation of chemical solutions was measured using auto level and levelling staff. The measurements were made before, during and after permeation of chemical solutions. After complete permeation, the test sites were cured for a period of 120 days. Both undisturbed and representative samples were then collected at different radial distances and depths and were brought to the laboratory for evaluation of physico-chemical, index, strength, swell-shrink characteristics and microstructure studies. The experimental results showed that the LPT technique reduced the swell-potential of the treated soils significantly in comparison to CaCl2 and NaOH solutions and lime slurry (LS). However, the swell potential values of LPT treated soils increased with increase in wet-dry cycles and attained an equilibrium at fourth cycle. CaCl2 and LS treatments were effective only up to two wet-dry cycles, and after which the swell increased and reached an equilibrium at 4th and 5th wet-dry cycles, respectively. In contrast, the NaOH treatment did not show any improvement in the swell behaviour with wet-dry cycles. The reduction inefficiency of LPT and LS treatments with increase in wet-dry cycles is due to the breakage of cementitious bonds with wet-dry cycles. Deep permeation stabilization studies showed that CaCl2, LPT and LS treatments were effective up to radial distances of 1.5d, 3d and 1.5d at all depths.