Resumen de Application of dynamic vibration absorbers on double-deck circular railway tunnels to mitigate railway-induced ground-borne vibration
This dissertation is concerned with investigating the efficiency of dynamic vibration absorbers (DVAs) as measures to mitigate ground-borne vibrations induced by railway traffic in double-deck tunnels. The main topics of the dissertation are the coupling of a set of longitudinal distributions of DVAs to the interior floor of a double-deck tunnel dynamic model, the computation of the response of this coupled system due to train traffic and obtaining the optimum design parameters of the DVAs to minimize this response. To address the first concern, a methodology for coupling a set of longitudinal distributions of DVAs to any railway subsystem in the context of a theoretical dynamic model of railway infrastructure is developed. The optimum design parameters of the DVAs are obtained using an optimization process based on a genetic algorithm. The effectiveness of the DVAs is assessed by two response parameters, which are used as objective functions to be minimized in the optimization process: the energy flow radiated upwards by the tunnel and the maximum transient vibration value (MTVV) in the building near the tunnel.
The model used to compute the former is a two-and-a-half dimensional (2.5D) semi-analytical model of a train-track-tunnel-soil system that considers a full-space soil model, and the one used to compute the latter is a hybrid experimental-numerical model of a train-track-tunnel-soil-building system. In the hybrid model, a numerical model of the track-tunnel system based on 2.5D coupled finite element-boundary element formulation along with a dynamic rigid multi-body model of the vehicle is used to compute the response in the tunnel wall, and then, the response in the building is computed using experimentally obtained transfer functions between the tunnel wall and the building. The triaxial response in the building is used to compute the MTVV. An alternative option to evaluate the MTVV in a building is to use a fully theoretical model of the train-track-tunnel-soil-building system. In the context of this modeling strategy, a computationally efficient method to calculate the 2.5D Green's functions of a layered soil is also presented. The results show that the DVAs would be an effective mitigation measure for railway-induced vibrations in double-deck tunnels as reductions up to 6.6 dB in total radiated energy flow and up to 3.3 dB in the vibration inside a nearby building are achieved in the simulations presented in this work.
