Study on the components and characteristics of seismic waves induced by blasting in adjacent existing tunnel
In order to study the influence of different components of blasting seismic waves on the safety of existing tunnel structures,based on the principle of polarization in seismology,combined with on-site blasting vibration monitoring and ANSYS/LS-DYNA numerical model,the components and characteristics of existing tunnel lining vibration waveforms were analyzed,and the correlation between dynamic tensile stress of existing tunnel lining and the peak resultant P-wave velocity was explored.The results show that the P-wave,S-wave and R-wave of MS1,MS3,MS5,MS7,MS9,MS11 and MS13 millisecond delayed blasting in the new tunnel all contribute to the particle vibration of the existing tunnel lining.The fastest propagating P-wave dominates in the early stage of each section,and S-wave and R-wave become the dominant wave patterns successively in the corresponding period.The location of seismic wave propagation path and vibration measurement point are closely related to the waveform components.Meanwhile,the particle vibration characteristics of existing tunnels corresponding to the excavated and unexcavated areas are significantly different.When L/D>1.58(L represents horizontal distance from the explosion source center and D represents tunnel clear distance),the maximum amplitude of S-wave in the unexcavated area exceeds that of P-wave and becomes the dominant waveform of particle vibration in the subsequent section.The dynamic tensile stress in the existing tunnel lining has a good linear correlation with the peak resultant vibration velocity of P-wave,and the safe vibration velocity threshold is determined to be 10.53 cm/s.
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