Lime piles and lime-stabilised soil columns, including the proprietary Colmix process, are reviewed in order to assess if they would be suitable treatments for improving slope stability on the ageing, clay earthworks of Britain's motorways. Lime and the effects of lime on clay soils are also reviewed. All the clays most at risk from slope instability would respond to lime treatment. It is concluded that, because they can increase the shear strength of the ground, both piles and columns have possibilities. A simple design method is given which indicates the direction, depth and spacing of piles or columns that would be required. (A)

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