Imaging ahead of a tunnel boring machine with DC resistivity: A laboratory and numerical study

Tunnel Boring Machines (TBMs) are used for tunneling and underground construction, by excavating material subsequently installing a segmental concrete tunnel liner support. However, unknown ground conditions pose significant risk to operations any damage the machine can be disastrous project. There is need tools which look ahead of TBM potential hazards during tunneling, such as water saturated zones, faults, boulders metal pipes. Geophysical methods offer capability image unexcavated in order avoid thus improve operations. In particular, DC resistivity method useful because it sensitive large range conductivity variations geological man-made materials. The research presented our paper consists three parts: (1) laboratory study system mounted on scale model within simulated environment, (2) series forward models studying different survey designs, (3) inversion imaging synthetic data under constraints. We introduce several new designs that attach electrodes probe (or probes), then pushed into earth front each time excavation stops. Our modeling results show using probes reduces interference caused metallic body, increases distance at target may detected. influence significantly reduced once 25% diameter negligible 50% machine. Depending specific design, targets detected from up 70% away. Finally, we invert produce ahead-of-tunneling images amounts prior information (e.g. geometry host resistivity) also time-lapse inversion. Numerical imaged with these distances 45% diameter.