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

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.