Bentonite slurries are essential for the operation of Slurry Tunnel Boring Machines (TBMs), helping to stabilize the excavation face, prevent soil collapse, and control groundwater inflow. This study examines the performance of a sodium-activated bentonite slurry used in tunnelling, focusing on its physical-chemical properties, rheological behavior, and interaction with soil. Tests were conducted to measure parameters such as unit weight, flowability, bleeding, fluid loss, filter cake quality, and pH. Rheological properties like apparent viscosity, plastic viscosity, yield point, and gel strength were also evaluated. Additionally, the interaction between the slurry and soil was analyzed to study the filter cake formation. The results showed that slurry with 5% bentonite performs well for TBM applications, offering strong stability, effective fluid loss control, and good rheological properties. This highlights the importance of optimizing bentonite slurries, future research could explore the potential of using additives to enhance performance to ensure safe and efficient tunnelling, especially in challenging ground conditions. 

Keywords: bentonite, bentonite slurry, TBM, tunnelling, rheology, Slurry Shield TBM.