ABSTRACT
Recently, tunnelling projects using the Tunnel Boring Machine (TBM) have been increased in South Korea. As for the Earth Pressure Balance (EPB) shield TBM, functional additives such as foam or polymer are sprayed and mixed with excavated soil. Conditioned soils by additives show improved flowability and workability, and thus can provide cutter wear reduction, face stability, material hauling facilitation, and other excavation efficiencies. In this study, rheological characteristics related to workability were examined for additive-conditioned soils. An artificially fabricated sandy soil was prepared by mixing silica sand 70% and illite 30%. Two types of additives, foam and polymer, were considered. Rheological characteristics were evaluated by performing the laboratory pressurized vane shear tests varying the Foam Injection Ratio (FIR) and the Polymer Injection Ratio (PIR). The vane torque, peak strength, and yield stress decreased as FIR increased or PIR decreased.
