Advantages of tunnel monitoring using distributed fibre optic sensing.

Predictive maintenance and safety assessment during the construction and operational phase are becoming more and more important in modern tunnelling. However, traditional measurement methods are often time-consuming, expensive and partially require an interruption of the tunnel traffic. In this article, we present a tunnel monitoring approach based on distributed fibre optic sensing (DFOS), which delivers hundreds of strain and temperature sensing points inside the structure and gives completely new information about the behaviour of the tunnel lining. Measurements can be performed automatically without the need of access to the tunnel and hence, monitoring can be made without disturbing the tunnel construction or operation. The developed system was installed within the shotcrete tunnel lining of a railway tunnel under construction in Austria. In addition to the critical installation process, this article discusses the main monitoring results and compares them to conventional measurements.