چكيده به لاتين
Due to the development and increase of intra-city rail lines, especially metro lines, the problem of the propagation of waves and vibrations caused by the movement of the rail fleet has become one of the challenges of railway engineering. In recent years, several methods have been proposed to reduce the vibrations caused by the movement of the rail fleet. The basis of all these methods can be summarized in such a way that changes and measures are implemented in the source of vibration or in the path of vibration or in the receiver of vibration to reflect or dampen part of the vibration. The use of vibration dampers or vibration absorbers in machinery and mechanical equipment and bridges has a relatively long history. However, the use of dynamic vibration absorber (DVA) in railway lines has received less attention and investigation. The use of vibration absorbers is important because it can reduce the vibrations reaching the ground level from the subway tunnel without making changes in the line and without blocking it. A review of the technical literature shows that there has been no study on the optimal DVA (mass, damping and natural frequency) characteristics to reduce the vibrations transmitted to the ground surface due to the passage of the subway fleet. In order to fill this research gap, in this thesis, using finite element modeling, optimal DVA specifications for different layers of soil around the subway tunnel have been obtained. In other words, by considering different specifications for the soil around the tunnel, a parametric study was done on DVA specifications. In this regard, the 2D finite element model of line-tunnel-soil was built in ABAQUS software. Plane strain element was used for all model components. Energy absorbing boundary conditions were placed on the boundaries of the model. In this research, using field test results and numerical studies of previous researchers, the finite element model was validated. The results of numerical model analysis showed that DVA in the best case reduces 35% of the maximum vibration acceleration, in other words, 4.5 dB of vibration acceleration on the ground surface. Using the results of the parametric study, diagrams have been presented to determine the mass, damping and optimal frequency of DVA according to the soil around the tunnel.
