The Properties and Structure of British Stiff Clays and Mudrocks
Lead Research Organisation:
Imperial College London
Department Name: Civil & Environmental Engineering
Abstract
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.
Publications
Ackerley S
(2016)
A system for measuring local radial strains in triaxial apparatus
in Géotechnique
Appolonia Gasparre
(2008)
Characteristics of London Clay: stiffness and influence of structure, a summary
Appolonia Gasparre
(2008)
Effects of recent stress history on a stiff natural clay
Brosse A
(2017)
The undrained shear strength anisotropy of four Jurassic to Eocene stiff clays
in Géotechnique
Brosse A
(2017)
Undrained stiffness anisotropy from hollow cylinder experiments on four Eocene-to-Jurassic UK stiff clays
in Canadian Geotechnical Journal
Brosse A
(2017)
The shear stiffness characteristics of four Eocene-to-Jurassic UK stiff clays
in Géotechnique
HOSSEINI KAMAL R
(2014)
The post-yield behaviour of four Eocene-to-Jurassic UK stiff clays
in Géotechnique
Satoshi Nishimura
(2008)
Simple shear testing of London Clay in hollow cylinder apparatus
Stephen Wlikinson
(2010)
The application of stereo E-SEM in understanding 3D mudrock structure
Description | The project investigated systematically the properties and development of soil structure of Oxford Clay, Gault Clay, Kimmeridge Clay and Lias Clay. These four mudrocks have geological ages ranging from Cretaceous to Jurassic and show widespread outcrops in England. The key objective was to understand how the properties and soil structure developed as a result of their depositional settings and post-depositional geologic processes such as diagenesis, overconsolidation and ageing. 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. A variety of experimental techniques was applied in the research including advanced microcharacterisation, mechanical destructuring, and advanced geotechnical mechanical testing to study and link the macroscopic mechanical properties to particle-level phenomena. It is shown that the geological processes experienced by these mudrocks have led to a range of mechanically important features including, hard pans of cemented material, variable features of fracturing and bedding, brittle response in shear, along with strong anisotropy in both small strain stiffness and shear strength. Recent geological processes including periglacial action, weathering and tree growth are also shown to have imparted significant changes to the engineering properties of these strata. The research generated three PhD Theses and a spread of Journal and Conference publications. It has led to a new understanding of, and a high quality data base for, these widespread sediments. The research will have a significant impact on construction activity in England, improving the cost-effectiveness and safety of many major projects. The work will also contribute to investigations of major new strategic issues including urban sustainability, nuclear waste disposal and carbon dioxide sequestration. The systematic understanding of the mechanics of these materials will aid the future development of constitutive models for a wide variety of stiff and aged argillaceous geomaterials. |
Exploitation Route | Direct use is also being made of the research by the academic and industrial geotechnical community. This includes particularly members of the steering group. One key example is the HS2 high speed rail project which is now making direct use of the data gathered. Another example is direct use by GCG of the testing on Oxford clay to help design the ground work for the Bodleian Library extension works at Oxford University. Other applications are likely to include caostal stability studies and the deevlopment of new nuclear power stations on Jurassic mudrocks. The work is being exploited by the readers of the academic papers that have been published in two major international conferences (Athens ECSMGE 2011 and IS-Seoul 2011). The first major journal paper has been published in the leading Journal Geotechnique and three others are under review that describe the work undertaken. A keynote paper has also been delivered at the specialist International Conference held in Buenos Aired 2015, leading to a major published summary. Two of the staff trained through the Grant are now employed in UK specialist consultancy (At GCG and initially Halcrow respectively) applying the findings from their work. One other is now employed as Lecturer in Geotechnics at the University of Liverpool and is undertaking related research at their Chinese campus. Use is also being made of the research by members of the steering group, including for example in work for the Bodleian Library extension in Oxford. The outcomes are likely to influence both academic and industrial contexts. A half day seminar was held at Imperial College in March 2012 devoted to reporting the Grant outcomes and attracted an audience of around 300 engineers and scientists. |
Sectors | Construction Energy Environment Transport |
Description | The research into UK mudrocks is feeding into the site investigations and design for the new HS2 high speed rail project. The HS2 line covers all of the strata considered in the study and the detailed information provided on their shear strength and stiffness anisotropy will be of great value in designing the tunnels, cut and embankment slopes and deep viaduct and bridge foundations required for the project. The PI has been engaged, through the UK Institution of Civil Engineers, as an adviser on the site investigation works and takes part in regular meetings and workshops. A request was made at the last workshop for data gathered in the three PhD studies to be forwarded to the project site investigation and design teams. In addition, the International Society for Soil Mechanics and Geotechnical Engineering's Technical Committee TC-101 on advanced laboratory testing invited the PI to deliver a keynote on the work to an international Conference held in Buenos Aires in November 2015, which resulted in a large written paper. Other papers have been prepared and are currently under review by Geotechnique, the leading international geotechnical Journal. Other potential applications for the work include coastal stability in parts of the UK and the ground conditions that will be encountered by future nuclear power projects. |
First Year Of Impact | 2013 |
Sector | Construction,Energy,Environment,Transport |
Impact Types | Economic Policy & public services |
Description | Collaboration on testing with Dr S Nishimura University of Hokkaido, Sapporo, Japan |
Organisation | Hokkaido University |
Department | Geotechnical and Material Engineering for Disaster Prevention |
Country | Japan |
Sector | Academic/University |
PI Contribution | We have shared data, tried out new methods of analysis and co-written publications |
Collaborator Contribution | We have carried out parallel testing in our two laboratories and also re-worked data from our earlier EPSRC grant, leading to new publications |
Impact | Three Brosse et al journal papers which are listed below Brosse, A., Hosseini Kamal, R., Jardine, R.J. and Coop, M.R. (2017) The shear stiffness characteristics of four Eocene-to-Jurassic UK stiff clays. Geotechnique. In Press. DOI: 10.1680/jgeot.15.P.236. Brosse, A., Jardine, R.J. and Nishimura, S. (2017) Undrained stiffness anisotropy from Hollow Cylinder testing of four Eocene-to-Jurassic UK stiff clays. Canadian Geotechnical Journal. In Press DOI: 10.1139/cgj-2015-0320 Brosse, A., Jardine, R.J. and Nishimura, S. (2017) The undrained shear strength anisotropy of four Eocene-to-Jurassic UK stiff clays. Geotechnique. Geotechnique. dx.doi.org/10.1680/jgeot.15.P.227 |
Start Year | 2014 |
Description | NERC British Geological Survey |
Organisation | British Geological Survey |
Country | United Kingdom |
Sector | Academic/University |
Start Year | 2007 |