Research on the deformation and settlement characteristics of tunnel lining structures under repeated loads

To study the deformation and settlement characteristics of tunnel lining structures under repeated loads, a tunnel lining structure model was designed. It was a reinforced concrete structural model, which can embed fibre optics in the structure. It was closer to actual tunnel engineering conditions. Repeated load experiments were carried out used an electro-hydraulic pulsation fatigue testing machine and a reaction frame. The crack development in specimens during the experimental process was analysed. The results of the distributed fibre optic monitoring were compared and analysed with those of traditional monitoring methods to verify the effectiveness and reliability of the distributed fibre optic monitoring results. Then, the longitudinal and circumferential strain results of the tunnel lining structure were analysed. The numerical simulations of the experiments were conducted by using finite element analysis. By comparing and analysing the simulation and experimental results, the correctness and effectiveness of the simulation calculation results were verified. On this basis, the deformation of the specimen in the static load test after different number of repeated loads and the influence of the loading frequency and repeated loading force on the deformation of the specimen in the static load test after repeated loads were analysed. The results show that the frequency of repeated loads has a relatively small impact on the specimen deformation. And the repeated loading force has a significant impact on the vertical displacement and deformation of the specimen. The research results can provide a theoretical basis and experimental data for the study on the deformation and settlement characteristics of tunnel lining structures under repeated loads.