Description: The Mercia Mudstone Group, part of the Triassic Series formerly known as the Keuper Marl, is a sequence dominated by mudstones that underlies much of central and southern England and parts of Northern Ireland, on which many urban areas and their attendant infrastructure are built. These strata affect the construction industry mainly in operations such as foundations, excavations and earthworks. When designing earthworks or structural foundations in, on or using Mercia mudstone, the designer needs to understand how the engineering properties are linked to the geological history. This report replaces report R47, and provides up-to-date information about the engineering properties of the Mercia Mudstone Group in order to improve the investigation, design and construction of ground engineering works in these materials.

It sets out the geological history and links this to the engineering properties for some regularly encountered design situations. Section 2 presents the geological history of the Mercia Mudstone Group and the mineralogy is explained in Appendix 2. Sections 3 to 8 review the geotechnical aspects and recommend good practice when testing and designing with mudstones of the Mercia Mudstone Group. The basic properties of the rock are outlined, and the more important developments in the understanding of the geotechnics of Mercia mudstones, since the early 1970s, are highlighted. In addition to the details of the references cited in the text, Appendix 1 provides a supporting bibliography of references relevant to engineering in the Mercia Mudstone Group. This report will be useful for geotechnical engineers, engineering geologists, civil and structural engineers, tunnelling engineers, highway engineers and construction professionals.

Keywords: soil-structure interaction, ground investigation and characterisation, ground engineering, piling.

Contents: 1 Introduction, 2 Geological background, 3 Properties affecting engineering behaviour, 4 Site investigation methods, 5 Correlations of engineering properties to the SPT, 6 In-situ properties and behaviour of Merca Mudstone, 7 Laboratory testing, 8 Design, construction and performance, 9 Concluding remarks, References, Appendices