Discussion on Papers 14 & 15

Dr. C. S. Dunn

Travers Morgan and Partners, East Grinstead

A considerable amount of information on Keuper Marl has been published by Chandler, Davis, Birch and others at Birmingham University but there are relatively few published case histories of failure. Mr Turner has therefore provided a useful study of a pavement failure on Keuper Marl. The problem with Keuper Marl is that like so many heavily overconsolidated clays of low plasticity it often gives the appearance of rock when first excavated. Everyone is surprised when it softens to such a weak state when it is unloaded and exposed by excavation and subjected to trafficking under poor drainage conditions. Keuper Marl generally has a high clay mineral content but this is present in aggregated beds and it actually behaves as a soil with a much lower clay content and the plasticity indices give a good indication of that behaviour.