Soil slaking under the effect of dispersants: characteristics and mechanism

The adhesion of clay to the cutterhead and cutters presents a significant challenge during earth pressure balance (EPB) shield excavation in clay strata. Dispersants are widely used to remove clay that adheres to metal surfaces, but their conditioning characteristics and working mechanisms have not yet been thoroughly investigated. This study investigated the effects of organic and inorganic dispersants on clay plasticity and slaking characteristics through Atterberg limit and slaking tests, complemented by Zeta potential and swelling tests to explore the underlying mechanisms. The results demonstrate that increasing the content of inorganic and organic dispersants reduces soil plasticity and enhances the slaking rate during the rapid development period in pure water. Dispersion slaking occurs in pure water for soil blocks treated with inorganic dispersant, while soil blocks treated with organic dispersant undergo primarily surface slaking. A higher organic dispersant concentration significantly intensified the slaking rate. In contrast, inorganic dispersant solutions inhibit soil slaking. Inorganic dispersant solutions impede soil expansion and slaking due to reduced electrostatic repulsion and increasing difficulty in water infiltration. Conversely, organic dispersant solutions accelerate soil slaking by promoting soil expansion and solution infiltration, reducing surface tension, and increasing pore air pressure.