Clogging during mechanical tunnel driving is not only a serious technical issue, but also an economic one. The costs of a tunnel excavation can easily rise and disputes between the awarding authorities and the executive companies may occur. Although the literature is full of cases describing the clogging in clayey soils and despite countermeasures being available, clogging still occurs. This study proposes an alternative method to diminish adhesion of clays on TBMs. Electro-osmotic flow experiments, spectral induced polarisation tests and Zeta-potential simulations were performed on kaolinite and smectite, mixed with several pore fluids under one critical consistency index. The results showed that the electrical parameters were not only influenced by the clay mineralogy per se, but also by the pore fluid chemistry. To apply the laboratory findings in in situ conditions, several theoretical considerations have been taken into account. Although further research is required, the study indicates electro-osmosis may be a new and revolutionary approach to deal with the clogging of TBMs.Résumé Le colmatage lors du creusement d'un tunnel est non seulement un grave problème technique, mais aussi une question économique. Ce travail de recherche propose une méthode alternative pour diminuer l'adhérence des sols argileux sur les tunneliers. Des expériences d'écoulement électro-osmotique, des essais de polarisation induite spectrale (SIP) et des simulations de potentiel zêta ont été effectués avec de la kaolinite et de la smectite, mélangées avec plusieurs fluides pour un indice de consistance critique. Les résultats ont montré que les paramètres électri-ques étaient non seulement influencés par la minéralogie de l'argile, mais aussi par la chimie du fluide interstitiel. Pour appliquer ces résultats de laboratoire aux conditions in situ, plusieurs considérations théoriques ont été prises en compte. Bien que des études supplémentaires soient nécessaires, on conclut que l'électro-osmose pourrait constituer une approche nouvelle et révolutionnaire pour traiter du problème du colmatage des tunneliers.

In geotechnical engineering, the clogging of clay soils can lead to serious problems. For example, during mechanical tunnel driving with tunnel boring machines, the problem of clogging is due to the excavated material, which sticks to the metallic parts of the machine, requiring cleaning, which in turn causes delays and financial losses. This article suggests a method to reduce adhesion of the excavated material on a steel surface by means of electro-osmosis. The adhesion of different clay types to a metal surface was studied in tilted plate tests. Three different clay samples were compacted and cut into slices with a thickness of 1 cm. Afterwards, both a direct current (DC) and pulsating DC, which consisted of the positive half-cycle only, were applied to the samples in order to study the influence of electro-osmosis on adhesion. The application of electrical fields caused the detachment of the clays from the metal surface by slight shear forces. It is not currently possible to determine the influence of the pulsating DC or DC on the detachment behavior of the clays because of the complexity of the system. However, the use of the pulsating DC results in a lower electrical contact impedance. The reduced pulsating DC contact impedance results in higher electrical currents (for the same applied potential difference) and thus a higher electro-osmotic efficiency (i.e., the energy needed to detach a clay from a metal

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