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On electrokinetic material response in marine clays

Final Report Summary - EMPIRIC (On electrokinetic material response in marine clays.)

The project set out to investigate means to manipulate sensitive natural clay materials in the laboratory to temporary obtain favourable hydro-mechanical properties. In the long-run this potentially reduces testing times in the laboratory by faster drainage rates and help inject stabilising agents in the clay matrix. The project mainly focused on technology enablers, by introducing unconvential methods for the sampling, characterisation and manipulation of sensitive natural clays. The social-economic impact, in soft soil areas around the world, is large: stabilising soft soil in land slide prone areas, limiting settlements of structures and infrastructure.

In the first half of the project a benchmark series of hydro-mechanical tests have been performed across the scales (i.e. nm to cm) on high quality block samples. The samples were taken in collaboration with the experts from the Norwegian University of Science and Technology (a new collaborator for the Marie-Curie fellow) which for the first time led to a systematic high quality study of sample quality on Swedish soils (Karlsson et al., 2016).

In order to test samples of various size and enabling application of electrical currents the existing commercial triaxial equipment needed to be modified. Here, the physical modelling expertise of the fellow helped realising a new triaxial cell that is actuated with ripple free syring pumps, originally developed for the microfluidics discipline with interchangeable syringes (size and material). This enabled testing miniature (2 mm diameter x 10 mm height) and large (50 mm diameter 100 mm height) samples at an improved control accuracy compared to the commercial equipment. Furthermore, by employing glass syringes the system could be electrically isolated. This novel test cell will be further developed for main stream testing. The novel use of the particular syringe pumps opened up a new application area for the German SME who originally developed the syringe pumps (the fellow helped advising a prospective client for the SME) (Publication in preparation).

For tracking changes in the clay material at the small scale two new techniques were successfully employed. For the first time 2D Digital Image Correlation and 3D volume correlation are introduced to element level testing of miniature samples to obtain the strain field in 1D plane strain compression tests. Image based techniques are not often completely understood by the geotechnical discipline. Hence the fellow, together with his existing collaborators in Australia, published a paper helping out the community on addressing some of the difficulties (Stanier et al. 2016). Another opportunity seized by the fellow was to perform 3D tomography tests in the 4D imaging laboratory lab of Dr Stephen Hall. Steve is a new collaborator with whom the fellow submitted a successful joint grant application to the Swedish Fundamental Science Council (€350k). The first results look very promising, but the low temporal resolution needs to be improved before conclusive insights can be drawn and the results be published. The latter requires a synchrotron X-Ray source. The fellow managed to get beam time in his first attempt at the European Synchrotron Radiation Facility in Grenoble (€24k) by for the first time collaborating with the leading group in the field in Grenoble (Drs. Edward Ando & Christophe Dano; University Grenoble Alpes) on a TEC-21 sponsored (€10k) grant directly after completion of the Empiric project.

Although 2D & 3D imaging techniques are very promising they still fall short for studying the chemical & structural changes at the clay agglomerate scale. Whilst initial tests with Raman Spectroscopy at Chalmers proved to be unsatisfactory (wrong wavelength) an alternative small angle X-Ray scattering technique proved to be more successful. In collaboration with Stephen Hall the fellow obtained 2 beam line grants at Maxlab III to study the changes in the clay due to mechanical manipulation and diffusion of salts into the clay matrix (Publication in preparation). He was the first staff member at his department to successfully acquire beam time for a Synchrotron Facility.

A considerable part of the project studied means to capture changes in the material due to elektrokinetics and nullify electrode effects (polarisation and corrosion where ions are dispersed in the clay matrix). Eventually, the use of artificial diamond electrodes proved most promising. The gathered measurement data proved to be inconclusive and more data will be gathered in future projects. With regard to measuring changes in the material the fellow abandoned the originally proposed Electrical Resistivity Tomography for at first instance bulk dielectric spectroscopy measurements (equipment co-funded by the €5k of the Åke och Greta Lissheds stiftelse). Due to the complexity of the research this is still ongoing in a follow up project on soil aging (to start in December 2016) which is a joint project with Dr Christophe Dano in Grenoble.

The growing Scientific reputation of the fellow led to a sponsored visit to work with Prof. Herle at the Technical Universität Dresden and two invited presentations. The first invitation was for Alert Geomaterials (The Alliance of Laboratories in Europe for Education, Research and Technology) to talk on trans-scale observations in sensitive clays (October 2016) and the second by the organisers of the Advancing Experimental Geomechanics workshop (Prof. Itai Einav at the University of Sydney) that collects the leaders in the field of geomechanical testing (November 2016). In the period of the fellowship he also got invited to the become a Member of the Technical Committee on Rock and Soil Mechanics of the European Society for Experimental Mechanics (chaired by Prof. Viggiani).

In addition to the scientific dissemination (papers and main editor of a conference proceeding) the fellow spent a considerable amount of his energy to help establish the Geotechnical Research Group at his host institution. He supervised 2 PhD students to completion as main supervisor, started three new projects (two in Collaboration with Prof. Karstunen), supervised a PostDoc in another EC project and visiting scientists from Norway and the Netherlands. Furthermore, following the fellowship he picked up some management duties to help restructure the organisation of the laboratory, and move the Civil & Environmental Engineering labs to the new location. In that role he will directly report to the Head of Department. Finally, he obtained supervision and teaching certification by successfully completing the designated courses at Chalmers University of Technology.

The fellow disseminated his expertise to professionals in society in Sweden via two mechanisms. In the first, as an active project leader for several projects funded by Trafikverket (>€400k as principal investigator), the Swedish Transportation Authority, he disseminates his knowledge to the problem owners and related symposia organised within this user group. He also had the opportunity to give an invited talk in 2015 at the Grundläggningsdagen an event for 700 practicing engineers in Sweden. Internationally, he gave a similar talk to end-users in Prague (organised by the Czech and Slovak Society for Soil Mechanics and Geotechnical Engineering) for about 50 participants in May 2016.

Finally, the fellow applied for the ERC starting grant and was even invited for interview in Brussels in May 2016, unfortunately he just missed out in this competitive grant scheme. Nevertheless without the financial support from the Marie-Curie fellowship, the candidate would not have found the time (and financing) to write such a successful grant application. Given these positive experiences with European funding he will continue to bid for EC funds.