An Idea to Simulate the Environmental Vibration Caused by Urban Rail Traffic

In most studies, the vibration source is modeled as random vibration with a given power spectral density at the nearest point from the rail, and the effect on buildings and human beings is further calculated by a two dimensional calculation. However, from 3 dimensional point of view, it is far away from the fact that the effect is come from many points along the rail while the trains move through rapidly. Two-step is defined to simulate environmental vibration. In the first step, the train-track system is simplified as a series of subsystems. Taking into account the track power irregularity, each subgrade reaction under ballast block was calculated when trains move on the track. All the forces constitute point source array to simulate the source. In the second step, the foundation is simulated as isotropic layered media, combined with artificial boundary conditions in the calculation border region, using the decoupling finite element method to calculate the surface environmental vibration. The simulation result was compared with those from field observation in Beijing, China. The result is quite close to the field observation data, and provides a good foundation for further study on environmental vibration impact to buildings and human beings.