Abstract
The adhesion of clay to the cutterhead and cutters presents a significant challenge during EPB shield excavation in clay strata. Dispersants are widely used to disintegrate clay adhering to metal surfaces, but their conditioning characteristics and working mechanisms remain elusive. This study investigates the effect 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 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 soil blocks treated with inorganic dispersant in pure water, while soil blocks treated with organic dispersant primarily undergo 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. The results may suggest injecting organic dispersant for removal of existing soil clogging in shield tunneling, but both inorganic and organic dispersants can serve to prevent the occurrence of soil clogging for shield tunnelling.