Tunnel monitoring

This chapter presents six case studies of tunnels instrumented with DFOS. These can be broadly divided into three categories. The first three case studies deal with the short-term monitoring of existing tunnels during proximity tunnelling. These tunnels have contrasting characteristics since the first two are over a century old and made with masonry arches and cast iron rings, respectively, while the last one is a new tunnel lined with concrete segments. The next two case studies deal with the instrumentation of tunnels during construction to assess performance and design assumptions. One of the tunnels made with sprayed concrete lining (SCL) was instrumented in situ while with the other one the concrete segments were instrumented off site during manufacture. The last case study introduces a recent and ongoing DFOS deployment aiming at the long-term structural health monitoring of some of CERN’s concrete-lined tunnels.