Assessment of the adhesion potential of kaolinite and montmorillonite using a pull-out test device

The tendency of clay particles to stick other surfaces means it is adhesive and can cause clogging of tunnel boring machines. Clogging arising from adhesion hinders or halts tunneling operations. The nature of adhesion in the interaction of soil and metal surfaces must be clarified in order to control its occurrence. This paper investigates the adhesion potential of clayey soil, specifically kaolinite and montmorillonite, by means of laboratory testing. A pull-out test device was used for testing and the test results revealed differences between minerals with respect to adhesion value and behavior. Montmorillonite showed 8 times greater adhesion than kaolinite in both their most adhesive forms. The time until dissipation of adhesion was 15 times greater for montmorillonite than for kaolinite. Montmorillonite adhesion increased and decreased in a bell-shaped curve as the degree of wetness increased. The curve for kaolinite was a gently increasing line. These differences are attributed to differences in the microstructural properties (e.g., CEC, SSA) and dominant sticking mechanism of each clay mineral. The consistency index (I _c ) for the most adhesive form of the minerals was 0.25 to 1.99 for montmorillonite and 0.15 to 1.19 for kaolinite. A chart was developed based on the results to illustrate the effect of I _c on the adhesion and clogging potential of the two minerals.