Durability Assessment of UK and Portuguese Jurassic Mudrocks

The term mudrock defines a large variety of fine-grained clay-rich sedimentary rocks. As these materials occur extensively they are often encountered in engineering projects, as natural ground on construction and ground engineering sites and as made ground, fill and construction materials. They may display a range of engineering behaviours controlled mostly by their composition and textural characteristics. In some situations, due to relatively rapid breakdown and susceptibility to volume changes they can cause problems both during and after construction. Investigation of mudrock durability can enable engineers to avoid problems, however prior assessment of mudrocks can be hindered if the weaker, less durable materials disintegrate during sampling and testing such that a biased view of the engineering behaviour of these rocks is formed. The paper presents durability assessments for UK Jurassic mudrocks that comprise the Lias, Oxford and Kimmeridge Clays formations. These mudrocks outcrop as a band stretching across England from the Dorset coast in the south west to the Yorkshire coast in the north east. The Portuguese Jurassic mudrocks studied are lower to middle Kimmeridgian in age that outcrop in the Arruda dos Vinhos Basin north/north-east of Lisbon. A review of the engineering properties of these UK and Portuguese Jurassic mudrock formations aims to compare the relationships, of the rocks of similar age, between the mineralogy, structure, strength and in order to investigate their similarities and differences in order to elucidate the controls on the durability of the different materials.