Electro-osmotic flow in clays and its potential for reducing clogging in mechanical tunnel driving

Abstract

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.

Modeling the evolution of complex conductivity during calcite precipitation on glass beads

“…13) and electro-osmosis (second term of eq. 13) (Bikerman 1940;Revil & Glover 1997;Heuser et al 2012;Leroy et al 2015). Because the diffuse layer is far (severalÅ) from the mineral surface and contains mostly counter-ions slowing down slightly counter-ions electromigration compared to co-ions (Bernard et al 1992), we assume that the ion mobility in the diffuse layer is similar to the ion mobility in the bulk water, that is β d i ≈ β w i (Lyklema & Minor 1998;Leroy et al 2008;).…”

Influence of surface conductivity on the apparent zeta potential of calcite

“…Heberling et al [9,10] also assumed that the thickness of the stagnant diffuse layer decreases with increasing salinity. This assumption is a typical signature of surface conductivity effects because the influence of surface conductivity on electrokinetic experiments decreases when salinity increases [25][26][27][28][29]. For instance, Heberling et al [9,10] assumed that the shear plane can be as far as 100−150 Å and 30−40 Å from the beginning of the diffuse layer at salinities of 10 -3 M and 10 -2 M NaCl, respectively.…”

The electrophoretic mobility of montmorillonite. Zeta potential and surface conductivity effects

“…accurately describing the EDL of clay minerals has many applications in environmental geoscience, geotechnics, and petroleum exploration [9][10][11][12]. Among clay minerals, montmorillonite (Mt), an important sub-group of smectite and the main constituent of bentonite, is characterized by particles with lamellar shape, very high specific surface area (typically comprised between 700 and 800 m 2 g -1 for perfectly dispersed particles), high surface charge density (of values usually comprised between 0.15 and 0.1 C m -2 ), and surface charge heterogeneity [13].…”