Electrical resistivity tomography survey for prediction of anomaly inmechanized tunneling

Anomalies and/or fractured grounds not detected by the surface geophysical and geological survey performedduring design stage may cause significant problems during tunnel excavation. Many studies on prediction methods of the groundcondition ahead of the tunnel face have been conducted and applied in tunneling construction sites, such as tunnel seismicprofiling and probe drilling. However, most such applications have focused on the drill and blast tunneling method. Few studieshave been conducted for mechanized tunneling because of the limitation in the available space to perform prediction tests. Thisstudy aims to predict the ground condition ahead of the tunnel face in TBM tunneling by using an electrical resistivitytomography survey. It compared the characteristics of each electrode array and performed an investigation on in-situ tunnelboring machine TBM construction site environments. Numerical simulations for each electrode array were performed, todetermine the proper electrode array to predict anomalies ahead of the tunnel face. The results showed that the modified dipole-dipole array is, compared to other arrays, the best for predicting the location and condition of an anomaly. As the boreholebecomes longer, the measured data increase accordingly. Therefore, longer boreholes allow a more accurate prediction of thelocation and status of anomalies and complex grounds.