Solution of Green function in near-field from high-speed railway seismic source and simulation signal analysis

Establishing and simplifying the high-speed railway seismic source model in near-field was crucial to analyzing the propagation law and energy radiation of high-speed railway seismic wave. With the forward calculation of Green function, the study on the simulation signal was carried out by MATLAB. By comparing the simulation signal with real signal, the Green function in the near-field term of high-speed-railway seismic source was verified to be reliable. In addition, according to simulation signal analysis on vibration curves, frequency spectra and energy distribution maps, the results showed that in the near-field of high-speed railway seismic source，the vibration curves were characterized with two peaks in the direction parallel to the high-speed railway, reflecting the propagation law of high-speed railway seismic wave under the moving-line source, while the propagation law and energy attenuation were obvious in the direction perpendicular to the ground surface. The high-speed railway seismic signal appeared broadband with clear discrete spectral lines, of which the feature frequencies varied from 60Hz to 370Hz, affected by the propagation distance of high-speed railway seismic wave. Within 150 meters, the energy of high-speed railway seismic wave under the feature frequencies below 200Hz attenuated greater, while when the high-speed railway seismic wave propagated farther than 150 meters, that under the feature frequencies between 200Hz to 300Hz attenuated much more. The energy distribution of high-speed railway seismic wave depended on the frequency response property at seismic source, and the frequency response property showed significant difference with the frequency ranging from 40Hz to 500Hz.