Laboratory study of fibre-optic strain sensor fixation for monitoring tunnel linings

Construction of increasingly challenging urban infrastructure requires new approaches for monitoring solutions. This paper presents a study of strain sensor fixation systems for monitoring the deformation behaviour of existing tunnels. Achieving the highest possible sensitivity of the system while maintaining the necessary sensor protection is one of the major challenges. Another challenge is to achieve a high readout resolution and high spatial resolution at the same time. Two series of tests were performed to assess different types of magnets and protection systems for fixation. Short-term tests were performed to determine the largest applicable force for the magnet fixation and to assess the accuracy of the system. The long-term tests were carried out to investigate the creep, slippage under the magnet between neighbouring sections and temperature effects.