PARTICLE-SCALE INVESTIGATION OF SEEPAGE INDUCED GEOTECHNICAL INSTABILITY

Lead Research Organisation: University of Sheffield
Department Name: Civil and Structural Engineering

Abstract

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Description Fluid tracking within a granular system has begun to enable local fluid velocities to be determined experimentally. Initial focus has been on monodisperse systems and has been extended to polydisperse systems and to different particle shapes. Comparison to CFD based numerical modelling has shown promise. In addition a triaxial permeameter has been developed with results on non-transparent outcomes but has yet to be used in transparent soil research.
Exploitation Route Transparent soil (i.e. use of refractively matched porous media) is an emerging technique used in a number of fields - geologic, geotechnic and rheologic. The outcomes on the behaviour of fluid flow inside both monodisperse spherical granular media and angular media will enable better consideration / validation of both conceptual and numerical models within soil mechanics.
Sectors Aerospace, Defence and Marine,Chemicals,Construction,Energy,Pharmaceuticals and Medical Biotechnology
 
Description This project progressed along two complementary strands. The work at Imperial College London (funded as EP/P010393/1) was numerical, while a complementary programme of experimental work was completed at the University of Sheffield (EP/P010423/1). The work at Imperial College London focussed on improving understanding of the behaviour of gap graded sands subject to shear deformation and on improving our ability to accurately and efficiently describe the fluid-particle interaction forces for coupled discrete element method simulations of densely packed soils. The numerical work exploited the discrete element method (DEM), finite volume computational fluid dynamics (CFD), and pore network models (PNMs). At Sheffield a novel technique was developed to image the three dimensional pore structure of a transparent soil while also recording the flow field. This work primarily focused on uniformly graded distributions constructed of spherical or angular particles and, preliminarily, on fluid flow fields within internally unstable gap graded distributions. This work was directly linked to computational fluid dynamics simulations at Imperial College London. The coupled simulation work at Imperial College was developed through interactions with Christopher Knight, a PhD student funded through the EPSRC Centre for Doctoral Training on Theory and Simulation of Materials (TSM-CDT - EP/L015579/1) and Dr. Ed Smith who was funded via the ARCHER eCSE scheme. Linked to this work at the University of Sheffield, was the creation of a stress-path flexible walled permeameter via a DTP funded position for Fahed Gaber, who gained his PhD in 2021 on "Investigation of seepage induced internal instability in dense gap-graded soils under complex states of stress". The work is relevant to geomechanics and to the broader particle technology / granular materials communities. Consequently, we have published our work in mainstream geotechnical journals (ASCE Journal of Geotechnical and Geoenvironmental Engineering, Géotechnique, Computers and Geotechnics) as well as Powder Technology which is a cross-disciplinary journal. Two PhD projects at Imperial College London emerged from the findings of the work. The first by Deyun Liu looked in a deeper manner at the distribution of stress in mixtures of sand, contrasting the distributions in mixtures with distributions in continuously graded materials. This project also explored how we can quantify the distribution of stress between the different size fractions in laboratory element tests. Key publications from this PhD include https://doi.org/10.1007/s10035-022-01215-9, https://doi.org/10.1680/jgeot.21.00127, https://doi.org/10.1061/(ASCE)GT.1943-5606.0002902, https://doi.org/10.1061/(ASCE)GT.1943-5606.0002466. The second PhD by Tokio Morimoto was funded via the MarieCurie MATHEGRAM ITN. This PhD explored the development of coupled DEM-PNM models for simulations involving both heat transfer as well as fluid flow. This work developed directly upon the PNM developments in EP/P010393/1. A key paper showing how an incremental improvement to the pore network model adopted can significantly improve predictions of the flow field is published (https://doi.org/10.1016/j.compgeo.2022.104900). A second paper looking specifically at the fluid-particle interaction force will be submitted in the Spring of 2023. A third PhD student, José Salomon, is now examining how to apply the coupled DEM algorithms developed in EP/P010393/1 to look at liquefaction. Work at Imperial College will start in the summer of 2023 to extend the modelling to partially saturated soils and non-Newtonian fluids. A research proposal has been submitted to EPSRC that will consider the flow of non-Newtonian fluids in sand will develop upon EP/P010393/1. A further, currently ongoing, PhD project emerged at the University of Sheffield from this research. This is a DTP funded study by Rowena Stevenson in which a rigid walled permeameter is placed under an enhanced g-field using geotechnical centrifuge acceleration. This study is focused on the determining influence of stress and stress gradient on the internal erosion of gap graded soil under downward flow, taking a "modelling of models" approach to ascertain fundamental scaling laws appropriate to fines migration. Dr. Hanqiao Che has continued to develop the unresolved DEM-CFD coupling algorithm and a paper in collaboration with the University of Birmingham will be submitted in the Spring / Summer of 2023. Dr. Fahed Gaber is preparing papers from his PhD on the influence of stress path and strain rate on internal erosion in underfilled and overfilled gap graded soils. Based on outcomes from the transparent permeameter research, Dr Bowman is currently preparing a chapter on techniques for Light Sheet Flow Imaging with Dr Joshua Dijksman, Soft Matter Physics, University of Amsterdam. In addition, the University of Sheffield hosted the 28th meeting of the European Working Group on Internal Erosion (set up under the auspices of the International Consortium on Large Dams, ICOLD) in July 2022, with approximately 40 visiting researchers from Europe, USA, Canada and Australia as well as representatives of a number of water companies (as reservoir asset owners) and the Environment Agency. Outcomes from this research featured as several extended abstracts and presentations. Papers are available at the following site: https://internalerosion.sites.sheffield.ac.uk/ The post-doctoral research staff working on the project have continued to develop their research. Dr. Adnan Sufian has an academic position at the University of Queensland, Dr. Ed Smith has an academic position at Brunel University, Dr. Hanqiao Che went on to work at the University of Birmingham, and Dr. Budi Zhao went on to an academic position at University College Dublin. Dr. Nicoletta Sanvitale is now a Research Associate at the University of Cologne. Dr. Fahed Gaber is now a Senior Design Engineer at Mabey Hire Ltd.
First Year Of Impact 2019
 
Description Collaboration between Imperial College and Sheffield 
Organisation University of Sheffield
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaboration between Dr. E. Bowman and Dr. C O'Sullivan is central to this project.
Collaborator Contribution Dr. E. Bowman and her team will provide the experimental data for this project.
Impact This is not a multi-disciplinary collaboration. We co-organized a kick off workshop for the project. Regular discussions are ongoing.
Start Year 2017
 
Description Collaboration between Imperial College and the University of Glasgow 
Organisation University of Glasgow
Country United Kingdom 
Sector Academic/University 
PI Contribution Dr. Tom Shire is a Co-I on this project.
Collaborator Contribution Dr. Shire is advising on the DEM simulations.
Impact This is not a multi-disciplinary collaboration. The ongoing discussion will inform the research outputs.
Start Year 2017
 
Description Collaboration with University of Nantes 
Organisation University of Nantes
Country France 
Sector Academic/University 
PI Contribution As a result of the experimental outcomes, Prof Didier Marot of University of Nantes and Elisabeth Bowman have set up a comparative experimental agreement. Data from internal erosion lab tests are being provided by U. Sheffield.
Collaborator Contribution Data from internal erosion lab tests are being provided by U. Nantes.
Impact None yet.
Start Year 2022
 
Description Collaboration with the University of British Columbia 
Organisation University of British Columbia
Country Canada 
Sector Academic/University 
PI Contribution Prof. J. Fannin is advising on the direction of the project.
Collaborator Contribution Prof. Fannin is discussing the detailed nature of the research based on his track record of experimental research.
Impact The collaboration is not multi-disciplinary. Discussions with Prof. Fannin are informing the direction of the research.
Start Year 2017
 
Description Convening / holding the European Working Group on Internal Erosion (ICOLD) Annual meeting at University of Sheffield 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The 28th meeting of the EWG-IE was held at the University of Sheffield over 3.5 days from 18th to 21st July 2022. This provided a forum for sharing novel
ideas and recent advances on topics related to internal erosion through water-retaining structures, such as embankment dams, levees and dikes, and in
their foundations. Researchers, scientists and engineers, from the private and public sector, in Europe and elsewhere were welcomed.
In line with previous meetings, the main discussion themes were: Internal erosion mechanisms and modelling; Laboratory testing and physical modelling; Field cases and observations; Inspection and monitoring; Risk assessment and management; Remediation of dikes and dams; and, Best practices and design guidelines.
Year(s) Of Engagement Activity 2022
URL https://internalerosion.sites.sheffield.ac.uk/
 
Description Participation in the European Working Group on Internal Erosion (ICOLD) Annual meeting 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact E Bowman made a presentation on this research at the Working Group meeting in 2019 and 2022 (Covid meant that the 2020 and 2021 meetings were postponed).
Year(s) Of Engagement Activity 2019,2022
 
Description Workshop on Seepage 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact On August 31 and Sept 1 a workshop on seepage induced instabilities was held at Imperial College London. The workshop was organized in conjunction with the British Geotechnical Association and the British Dam Society. The workshop was also supported by three technical committees of the International Society for Soil Mechanics and Geotechnical Engineering: TC 105 Geo-Mechanics from Micro to Macro, TC 201 Dikes and Levees, and TC 213 Scour and Erosion. The workshop was organized to launch the EPSRC funded collaboration between Imperial College London, the University of Sheffield entitled "Particle-Scale Investigation of Seepage Induced Geotechnical Instability", and the EPSRC provided financial support for the workshop. There were 48 participants including representatives from consulting engineers, dam owners and academics.

The first session of the workshop focussed on UK practice. The first speaker, Rob Gilbert from ARUP, reminded us all how international UK practice is, describing case histories of dams in Myanmar, Mauritius and Sudan. Dr Toby Roberts from WJ Groundwater presented a number of dewatering case histories and discussed some of the issues associated with filter selection for dewatering wells. Dr Chris Menkiti from GCG presented some case histories from the Warsaw Metro. Dr. Menkiti also highlighted the problem of sea borne transport of mineral ores; instabilities associated with this material have resulted in the loss of a number of large ships in recent years.

The second session of the workshop was loosely based around a consideration of design guidance and codes. The first speaker was Dr Brian Simpson from ARUP, who has been involved in a working group looking at seepage related issues in EC7. Dr Philip Smith from Royal Haskoning DHV spoke about his experience with UK levees (flood embankments) and introduced the Levee Handbook. Dr Bernard Odenwald provided a German perspective, while Mr. Rod Bridle introduced the ICOLD Bulletin 164 on Internal Erosion.

The second day of the workshop was research orientated. In the first session, there was a focus on international experimental research, with presentations from Prof Jonathan Fannin (University of British Columbia, Canada), Dr Didier Marot (University of Nantes, France) and Prof Akihiro Takahashi (Tokyo Institute of Technology, Japan). The final session of the workshop outlined UK research, and started with a presentation from Dr Philippe Sentenac (Strathclyde) on field monitoring of internal erosion in flood embankments. Finally, the joint Sheffield - Imperial research project team gave presentations on transparent soil and discrete element modelling.

Key points from the workshop were:

• There was a repeated theme in the industrial presentations of the need to understand both the geology of sites as well as the history of human intervention at sites, whether the site is an existing levee or a new deep excavation in an urban environment. Dr Smith and Dr Odenwald highlighted that failures are also often observed at irregularities (transitions) or junctions with structures intercepting levees.

• There is scope for new technologies to help us better understand site conditions: Dr Philip Smith from Royal Haskoning DHV highlighted the ability of LIDAR to help identify old meanders and old drainage channels. Dr Sentenec discussed the use of geophysics, focussing on electrical resistivity tomography and describing use of this technology on flood embankments in France.

• The risk posed to dams and flood embankments by internal erosion was highlighted. Considering the performance of embankments in England since 2007, Dr Smith highlighted that the particular threats to UK levees are seepage, internal erosion and uplift; however, with extreme floods such as those in the winter of 2015/2016 overtopping is also an issue. He noted that these mechanisms pose a greater risk to levees than slope stability failures.

• Dr Simpson pointed out that factoring water pressure under using an EC7 approach can lead to impossible situations.

• Dr Smith highlighted the fact that despite the significance of levees, in contrast to dams, there is less legislation and inspection. Dr Smith pointed out that these structures are vulnerable as they were typically not designed to particular standards and are often constructed on poor ground; their fragility is typically not apparent. To emphasize how fragile these structures can be, Dr Smith showed a video of a US Corps of Engineers experiment in which a full-scale levee on silty sand failed only 15 minutes after the development of a pipe beneath the levee.

• Mr. Bridle explained that the ICOLD bulletin on internal erosion is very useful to engineers seeking to understand the mechanics of internal erosion; notably they define the four mechanisms, suffusion, backward erosion, contact erosion and concentrated leak erosion. He highlighted that each mechanism can fundamentally be considered as a load - resistance problem. He pointed out that the challenge is to estimate the hydraulic forces causing erosion in vulnerable soils.

• Prof Fannin explained that in seeking to improve understanding of internal erosion in embankment dams there is a need for both data completeness and model completeness.

• Prof Marot proposed that in assessing suffusion (one form of internal erosion) the power expended by the seepage force should be considered.

• Presentations from Dr E. Bowman (Sheffield) and dir. T. Shire (Glasgow) demonstrated the power of transparent soil and discrete element modelling to examine the fundamentals of seepage-induced instabilities.

• Recent guidelines and resources for practicing engineers were highlighted including The International Levee Handbook, ICOLD Bulletin 164 on Internal Erosion, the German BAW Codes of Practice.

Selected presentations from the workshop are available at http://www.imperial.ac.uk/geotechnics/research/research-projects/seepage-induced-geotechnical-instability/seepage-workshop/. For further information, contact Prof Catherine O'Sullivan (cath.osullivan@imperial.ac.uk).
Year(s) Of Engagement Activity 2017
URL http://www.imperial.ac.uk/geotechnics/research/research-projects/seepage-induced-geotechnical-instab...