Improvement of clay soils using lime piles

The challenges posed by expansive soils to civil engineering structures in terms of damages and billions of dollars loss to repair and maintenance have been the major concern of 21st century researchers. In the last decades, lot of research works had been done to find feasible solutions to these problems. The challenges that the problematic soils caused are linked to their inappropriate engineering properties such as swelling, shrinkage, strength, and compressibility. The deficient properties of the expansive soils are attributed to the nature of their mineral type, structure, pore sizes, pore ionic solution etc. In order to transform the deficient properties to desirable properties required for engineering designs and applications, there is a need for a safe, economical and long lasting deep soil stabilization technique(s). In this study, a detail laboratory program was performed on a typical expansive soil to examine its physical and engineering properties in its natural state and when stabilized with a lime-pile technique. Five lime-piles of 3 cm each in diameter and 30 cm in height were constructed to stabilize the soil block which is 40 cm in diameter and 36 cm in height. The lime (Ca2+ ions) migrated from the piles into the soil block at different curing periods of 28, 90 and 120 days and produced different stabilized soil aggregates at different lime-pile distances. Extensive laboratory tests such as CBR and electrical resistivity were performed on the natural and the stabilized soils extracted at different lime-pile distances and curing periods and the test results were compared and discussed. The results of the tests indicated significant changes in the physical and engineering properties of the stabilized soils compared to the natural soil. The CBR test results suggest that the stabilized soil in 120 days of curing is fair enough to be used as both subbase and subgrade for highway and foundation iv constructions. The electrical resistivity measurements of the natural and lime-pile modified soils indicated that with lime treatment and curing time, the electrical resistivity of the lime treated soils decreased due to the particle aggregation and flocculation. The electrical resistivity (ER) test results suggest that the ER measurements can be used as a monitoring technique for lime diffusion in in-situ lime-pile applications. Keywords: aggregation, electric resistivity, expansive soil, flocculation, lime piles.