A new pressurized vane shear apparatus

The new vane shear test apparatus enables shear strength investigations of fine-grained soils at different pressures and shear velocities, such as those acting in a working chamber of an Earth pressure balance tunnel boring machine. The main conceptual innovation is the application of a confining pressure onto the test specimen while the vane shear test is performed. This allows for the exploration of pressure dependency on the shear strength of fine-grained soils, e.g., conditioned with foams and polymers. The technical innovation is that the torque sensor is located inside the pressure chamber. This permits for accurate torque measurement by excluding friction at contact areas and sealed insertions. The new vane shear test apparatus is a fast and reliable device to measure the shear strength of any fine-grained soils with soft consistency. In this paper pressure and rate-dependent shear strength data of kaolinite and illite clays and of "conditioned soils" made of kaolinite and illite clays mixed with foam and polymer additives are presented and the applicability of the apparatus is validated.