Research on the deformation and settlement characteristics of tunnel lining structures based on distributed fibre optic sensing technology

To study the deformation and settlement characteristics of tunnel lining structures, a tunnel lining structure model was designed based on distributed fibre optic sensing technology. Compared to the cylindrical model used in traditional tunnel lining structural model experiments, in this study, a reinforced concrete structural model was adopted, which can embed fibre optics in the structure, which is closer to actual tunnel engineering conditions. Central and symmetrical concentrated loading experiments were carried out with a simply supported reaction frame. The results of the distributed fibre optic monitoring were compared and analysed with those of traditional monitoring methods to verify the reliability of the distributed fibre optic monitoring results. The numerical simulations of the experiments were conducted by using finite element analysis. By comparing and analysing the simulation and experimental results, the correctness of the simulation calculation results were verified. On this basis, the impact of concrete strength, circumferential reinforcement spacing, and longitudinal reinforcement strength on the deformation and settlement of the tunnel lining structure were analysed. The results show that the hierarchical effect of the strain monitoring results obtained by the embedded fibre optic is more obvious, indicating that the radial monitoring effect of the embedded fibre optic on the tunnel structure is less affected by other external factors than the strain gauge, and the monitoring data are more accurate and effective, with good engineering characteristics. Improving the concrete strength, appropriate circumferential reinforcement spacing, and increasing the longitudinal reinforcement strength can effectively enhance the ability of the structure to resist deformation at the stress location. These factors play a significant role in improving the overall resistance to deformation and safety of the structure. The research results provide a theoretical basis and experimental data for the application of distributed fibre optics in monitoring the deformation and settlement of tunnel lining structures.