Abstract: Tunnel settlement is an important index to evaluate the safety and stability of tunnel structure. Distributed optical fiber monitoring technology can obtain the strain distribution of the measured parts of the structure, but it cannot directly reflect the settlement of each part of the tunnel. In this paper, a tunnel settlement inversion model based on distributed optical fiber strain is proposed to link the optical fiber strain curve with the tunnel settlement curve. The feasibility of the model is verified by theoretical derivation, numerical simulation and laboratory tests. Through the distributed optical fiber monitoring project of the 07 bid of the new airport line of the new Beijing rail transit line, the strain curves of the tunnel vault are obtained under different working conditions during the period of dismantling temporary shoring of the tunnel. The settlement of the vault of the tunnel is calculated based on the optical fiber strain curve with the help of the tunnel settlement inversion model. The calculated results are in good agreement with the measured results of the construction monitoring center, and the error is within the acceptable range. The research results can provide theoretical and experimental bases for the application of distributed optical fiber sensing technology in tunnel settlement monitoring.

Key words: distributed optical fiber, monitoring technology, strain sensing, settlement monitoring