ABSTRACT
Safety during tunneling is one of the main challenges of underground construction. The key concern is to avoid confinement losses leading to large delays, costly additional works and higher insurance costs. Here classical surface instrumentation should be improved in order to get early warning and, therefore, early decision making regarding the operating parameters of tunnel boring machines (TBM). One original concept proposed in the framework of the Tunconstruct project, consists in very early settlement detection close to the tunnel crown and before any detectable effect occurs on the surface. The proposed solution is to set-up a sensing element inserted into a borehole drilled above the foreseen tunnel.
