Laboratory simulations on hybrid non-destructive survey of electrical resistivity and induced polarization to predict geological risks ahead of a TBM tunnel

It is essential to predict geological risks ahead of a tunnel face during tunnel boring machines (TBMs) excavation to ensure efficient and stable tunnel construction. In this study, a series of lab-scale chamber experiments were conducted to simulate the electrical resistivity and induced polarization (IP) surveys during TBM advancement toward hazardous ground conditions. Various hazardous ground conditions (i.e., fault zones, water intrusion, geological transition, embedded core-stone, and cavities) possibly encountered during tunnel excavation were modeled in the soil chamber. The electrical resistivity and chargeability were simultaneously measured at the tunnel face modeled in the laboratory chamber during tunnel excavation. Guidelines for accurately predicting the hazardous conditions were proposed by analyzing the patterns and variations in resistivity and chargeability measurements corresponding to the TBM advancement. Note that the combined approach simultaneously implementing the electrical resistivity and IP surveys can predict hazardous ground conditions ahead of a tunnel face, which allows safe tunnel excavation by minimizing the potential risks in advance.