The effects of soil conditioning agents on fine and coarse-grained soils with applications in earth pressure balance machine tunnelling

Foaming agents, often used in Earth Pressure Balance Machine (EPBM) tunnelling, can have a fluidising effect on soil, creating a homogeneous soil with a consistency that maintains the necessary support/face pressure, and reduces the permeability and stickiness of the soil, specifically clays.; Slump tests were conducted to determine the macro-scale effects of foaming agents on kaolinite and coarse sand, while zeta potential and conductivity measurements were conducted on kaolinite to determine the micro-scale effects.; The raw slump test results did not accurately depict the effects of the foaming agents, indicating the unreliability of the testing method in this case. The results obtained with the DT-1200 Acoustic and Electroacoustic Spectrometer showed no practicability at the surfactant concentrations used in tunnelling projects, and did not accurately depict the microscale effects of the surfactants. Nevertheless, the use of surfactants increased the flowability in both soils, and decreased the stickiness in kaolinite.