Investigating Inherent Mechanism of Loess Adhered to Shield Machine Cutting Tools

Soils adhered to cutting tools or clumped to each other could not only cause a low advance rate in tunneling but some difficulties in spoil discharging. These especially hold true while tunneling in the loess containing primarily silt particles. The above remains to be addressed toward preventing unplanned downtimes and additional project costs. In addition to the mixing and fluidity tests, the AFM (atomic force microscopy) test is applied to explore the inherent mechanism affecting their adhesion properties when sand, kaolinite, and montmorillonite are applied as adhesion reduction materials. The adhesion ratio is in a negative relation with the fluidity. The latter two are not deemed good adhesion reduction materials despite the higher adhesion force of the sand-loess mixture than the kaolinite-loess mixture. The intermolecular force plays a key role in triggering such a phenomenon. The highest adhesion force of 52.5 nN is attained by the montmorillonite-loess mixture due to the development of capillary force.