摘要

The vibration-based SHM (Structure Health Monitoring) system has been successfully used in bridge and other surface civil infrastructure. However, its application in operation tunnels remains a big challenge. The reasons are discussed in this paper by comparing the vibration characteristics of the free tunnel structure and tunnel-soil coupled system. It is revealed that all the correlation characteristics of the free tunnel FRFs (Frequency Response Function spectrum) will vanish and be replaced by a coupled resonance frequency when the tunnel is surrounded by soil. The above statement is validated by field measurements. Moreover, the origin of this phenomenon is investigated by dispersion analysis based on a novel simulation model termed as TTMM (Timoshenko beam-Transfer Matrix Method). It is proved that the coupled resonance frequency occurs at the intersection of soil and free tunnel flexible wave mode dispersion curves. A simplified method is developed to determine the relationship between the tunnel Young's modulus and the coupled resonance frequency, which can be employed as an index for quantifying the tunnel global stiffness.