Fixed-point excitation prediction method for environmental vibration of urban rail transit

In urban rail transit construction, the empirical prediction equation is generally used to predict the environmental vibration along the line after its operation. It is used as the basis for whether to adopt a vibration-damping track or which vibration-damping track to use. Due to the superposition of complex factors such as geological conditions, differences in vehicles, and their running foundations on the prediction results, the track implementation should be considered at least with a design margin of 3 dB. However, there are still a large number of environmental vibration complaints. Therefore, an ecological vibration prediction method with higher prediction accuracy is proposed. The construction of the track-foundations, such as tunnel, bridge, and roadbed is completed. Before the track system is constructed, a fixed-point excitation load simulating the passage of trains is applied on the track-foundation, and the vibration-sensitive points around the line are directly measured by the actual measurement-environmental vibration prediction evaluation. The fixed-point vibration source function model for simulating train passing is deduced as the excitation load applied to the track-foundation; the fixed-point vibration source foundation finite element model and vehicle-track-foundation coupled dynamic model with the same track-foundation and foundation model have been established. The vibration response of the track-foundation and foundation surface when the train passes through is calculated separately. The results corresponding to different prediction methods of environmental vibration are compared and analyzed. The comparison between the theoretical prediction value of vibration response, the prediction value of the empirical equation, and the measured value shows that the vibration response waveform of the foundation surface is the same as that of the actual train passing under the action of the fixed-point vibration excitation source function. The vibration prediction error is much smaller than the empirical equation predicts the result. It shows that the prediction accuracy of the fixed-point excitation prediction method for environmental vibration is higher than that of the existing practical equation method. Because the fixed-point vibration source device is simple to implement and the ecological vibration field testing method is mature, it is beneficial to the field application of the fixed-point vibration excitation prediction method for urban rail transit environmental vibration.