Abstract

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 surface by electro-osmosis is significantly lower for pulsating DC than for DC). The sample and contact impedances were determined by electrical impedance spectroscopy measurements.

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