Study on the mutual interference and propagation characteristics of three-dimensional vibration during shield tunnel construction in hard rock strata.

Vibrations generated by shield tunnel construction in hard rock strata can have adverse effects on the surrounding environment. To investigate the mutual interference of three-dimensional vibrations and the propagation characteristics of vibration waves during the construction process, this study is based on the shield tunnel project of a Jinan urban rail transit construction zone. The research integrates on-site vibration monitoring, FLAC3D numerical simulations, and theoretical analysis of transfer functions. The results show that: 1)Single-direction vibration input has the greatest impact on the output in the same direction, with minimal interference in the other two directions. A vibration input in one direction generates new harmonic components not only in the same direction but also in the other two directions.2)Vibration generated by shield tunnel construction shows a stronger correlation between the vibration wave propagation speeds in the tunneling direction of the shield machine and the direction perpendicular to the tunneling direction.3)When only a single direction of vibration signal is input, the waveform of the output vibration signal at the monitoring point is similar to that obtained with simultaneous input of three-direction vibration signals, but there are differences in the vibration speed values.4)The vibration monitoring signals from the building pile foundation exhibit periodicity over time, with fluctuations. As the distance from the excavation surface increases, the peak vibration speed decreases, the decay rate slows, and the arrival time is delayed.5)The peak vibration speed at the monitoring point after the shield machine passes is slightly higher than before its passage. The arrival time of the vibration wave at the monitoring point is later after the shield machine passes.6)For vibrations at different locations of the same pile foundation, the vibration speed at the same depth near the tunnel center is the highest. When the distance from the excavation surface is the same, the vibration speed near the bottom of the pile is slightly higher than that at the middle of the pile.