Research on Vibration Propagation Characteristics of Tunnel-Stratum System Based on Vibration Exciter Test in Tunnel

The pulse vibration excitation experiment is carried out in the tunnel with a depth of 18m by using the automatic drop-weight excitation device. The vertical vibration acceleration is measured at 15 measuring points with equal spacing on the ground surface. The time history, the frequency spectrum of the tunnel-stratigraphic system under pulse excitation and the propagation law and attenuation characteristics in the octave is studied. The results show that: (1) the transmission loss of vibration acceleration at the measurement point from the tunnel wall to the surface at 0m is above 35dB, and the soil has a strong attenuation effect on the vibration wave propagation; (2) there is an obvious ground vibration amplification area at the 20 similar to 25m on the ground, and the amplification area appears at the place where the horizontal distance between the surface measurement point and the tunnel is almost the same as the buried depth. (3) With the increase of frequency, the vibration spectrum and frequency response function curve show "fluctuation reduction" form; (4) As the horizontal distance increases, the vibration energy attenuation of the frequency band below 10 Hz decreases, and the frequency band above 10 Hz exhibits obvious vibration energy attenuation.