Effect of dispersant on the tangential adhesion strength between clay and metal for EPB shield tunnelling

When Earth Pressure Balance (EPB) shields pass through clayey ground, the working tool is frequently clogged, causing a low tunnelling rate and accelerating cutter disk abrasion. Clay clogging is considered to be due to the high tangential adhesion strength between the clay and metal. This paper investigates the changes in the tangential adhesion strength with the consistency index under different total normal stresses and with different dispersant contents using a mixture of bentonite and kaolin (mass ratio of 1:1). The results showed that the tangential adhesion strength first decreased significantly and then remained almost constant with an increase in water content. Injection of the dispersant could decrease the tangential adhesion strength of clay. The tangential adhesion strength decreased gradually with a lower dispersant content (