Physio-chemical changes in clay caused by ion migration from lime piles

Migration of ions from lime piles to bring about improvements in clay soils, into which the lime piles have been installed, has been observed by several researchers. Specific measurements have been taken to show how effective the improvement has been (in terms of distance, time, and magnitude of the physical change), and yet the observations have yet to be adequately explained. This paper aims to examine, via a series of controlled laboratory experiments, the physico-chemical phenomena in London clay brought about by the ion migration from a lime pile having the same initial water content as the clay. Ion migration was shown to occur under a combination of three drivers (chemical, electrical, and hydraulic gradients), the importance of each being discussed. Changes in the clay's properties were determined by shear strength, using a novel fall cone technique, and plasticity measurements, while measurement of pH, conductivity, and ion concentrations proved vital to understanding the processes taking place, notably in relation to the cation exchange and clay mineral dissolution effects of classic stabilization.