The Properties and Structure of British Stiff Clays and Mudrocks

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Soil structure is generally regarded as the combination of fabric (i.e. particle arrangement and association) and interparticle forces (e.g. bonding, cementation, but excluding those of purely frictional nature). The structure of natural sedimentary clays starts to develop during initial deposition, and evolves over geological time. Sedimentation structure refers to features created as the state of a soil moves down the sedimentation compression curve while post-sedimentation structure refers to that created after burial and perhaps subsequent unloading, during a period of prolonged stasis, and would include any effects of tectonic loading on the soil. The project investigates in a systematic way the development of soil structure in stiff clays and mudrocks from England with geological ages ranging from Triassic to Cretaceous, including any four from Mercia Mudstone, Lias Clay, Oxford Clay, Gault Clay and Kimmeridge Clay, in order to understand the development of soil structure along with the post-depositional geologic processes such as diagenesis, overconsolidation and ageing. A variety of experimental techniques will be used, including advanced microcharacterisation, mechanical and chemical destructuring, and geotechnical mechanical testing, in order to determine explicitly the microstructure and to link the macroscopic mechanical properties to particle-level phenomena.The stiff clay and mudrock sediments are widespread in England and the potential impact of this research will be significant to the construction industry in terms of the economy and safety of many major projects. The work will also contribute to investigations of major new strategic issues of urban sustainability, nuclear waste disposal and carbon dioxide sequestration. A systematic understanding of the mechanics of these materials will also assist the future development of constitutive models for stiff clays and mudrocks.