DEEP-SLOPE STABILIZATION USING LIME PILES

Lime piles have been successfully used in practice in several countries worldwide but their mechanism of operation has not been adequately explained. The literature on the subject has been briefly reviewed and a list of suggested stabilizing processes has been compiled. Programs of experimental work to investigate each process are described and the results are presented. Lime piles, which usually consist of columns of quicklime placed in pre-formed holes in clay soils, draw in water during hydration and expand. No lateral consolidation of the surrounding clay occurs, however, because of the stoichiometry of the hydration reaction. The water loss in the surrounding clay causes an increase in undrained shear strength. The associated pore water pressure reduction, or suction, caused by the hydration reaction is shown to be significant in the short term to increase the stability of the slope and in the long term by overconsolidation of the shear plane. Migration of calcium and hydroxyl ions from the piles has been shown to be limited to less than 30 mm (1.2 in.), as might be expected from considerations of clay liners. The pile itself is shown to have significant strength. The laboratory work has heen supported by the initial findings of a program of field trials.