The 23rd Glossop Lecture: Mud to rock and back

As mudrocks underlie large areas of the UK, including major urban areas and infrastructure routes, they frequently form the bedrock at construction sites and slope and tunnel engineering works. They may also be used as fills or construction materials. They range widely in terms of strength and compressibility, depending on composition, degree of compaction and induration, weathering grade, fabric and structure. A review of the performance of mudrocks in engineering situations including slopes, tunnels and in embankment and foundation construction highlights the importance of durability and the role of chemical weathering processes, especially the oxidation of pyrite, in the engineering performance of these materials. It is necessary for the effects of changes in the environment of mudrocks, brought about both during and after completion of engineering works, to be anticipated early in projects so that design and construction measures that circumvent or avoid problems can be adopted. Advances in the understanding of factors controlling mudrock durability that can facilitate improved prediction of changes in properties are described. It is argued that understanding controls on the properties of mudrocks underlies ways of avoiding the problems that can arise in civil engineering works involving these materials. It is apparent that there is much to be gained from the publication of case histories of past engineering projects, particularly those in which problems stemming from unexpected changes in the properties of mudrocks have occurred.