Laboratory trial mixes for lime-stabilised soil columns and lime piles

Laboratory trial mixes of clay and lime, clay and lime plus cement, and of pure lime have been prepared, and specimens made from the mixes have been tested for strength, with the aim of assessing their suitability for use in a full scale field trial of lime-stabilised soil columns and lime piles. The clays used were Gault Clay and London Clay and the trial mixes had 5, 10 and 15% lime, and 5% lime plus 5 and 10% cement. Pure quicklime was also tested. The results showed that all the additions of binder studied had the effect of increasing the strength of the soils, but that the mixes with lime did not attain enough strength to be suitable for lime-stabilised soil columns. However, the mix of London Clay with 5% lime plus 5% cement was strong enough for this purpose. The strengths of both unlined and lined piles made from compacted quicklime installed in clay were high enough for these piles to be suitable for slope stability improvement, but the strength of unlined lime piles installed in sand was too low, raising doubt as to the ability of quicklime to harden in all circumstances. Test showed that there is much advantage in using waterwell screen pipe as a lining for lime piles. Pre-fabricated lime piles made from sections of waterwell screen pipe pre-packed with quicklime are foreseen to have even more advantage in use. Recommendations are made for the full-scale field trial that is to follow, and these include a trial of the use of pre-packed lime piles to see if the idea is practicable. (A)