SYMPLECTIC MODEL AND ITS APPLICATION OF VERTICAL ENVIRONMENT VIBRATION PREDICTION ABOUT VEHICLE-TRACK-TUNNEL COUPLED SYSTEM

By combining the random vibration Pseudo Excitation Method (PEM), symplectic mathematics of infinitely periodic sub-structures, and harmonic response finite element analysis, a prediction model of environment vertical vibration induced by a vehicle-track-tunnel coupled system is proposed which accounts for the frequency-dependent stiffness of the rail pad. Taking Nanjing's Metro Line 1 Project as the research object, a Martin-Davidenkov model, a type of equivalent linear visco-elastic model, was used to describe the relationship between soil loading and unloading and nonlinear stress-strain. Theoretical results of vertical acceleration of the surface soil are compared with the measured data, and they agree well in the whole frequency domain but have a maximum peak difference of 0.6 dB at the centre frequency of 50 Hz. The conclusion indicates that the track irregularity on the testing subway line is close to the calculated condition, and the prediction model for environment vertical vibration of the vehicle-track-tunnel coupled system has better predictive accuracy and efficiency in the frequency domain and its parameter selection method is reasonable.