Abstract

In general, discussions concerning noise problems due to blasting excavation of the tunnel focus on the noise caused by the sound propagated by air vibrations. However, sometimes the noise that the ground vibration causes might become a problem. This noise is called a solid-borne sound.

When the solid-borne sound caused by blasting vibration occurs inside a house, acoustic radiation takes place at the floor, walls, and ceiling of the living space as the house vibrates. The intensity of the sound can increase depending on the dominant frequency of vibration. It is important to note that especially when the ground is hard and has little discontinuity, the noise is generated by the unrecognizable ground vibration because the vibration is transmitted far away without the high frequency components attenuating.

In this study, we report the case of the acoustic radiation (solid-borne sound) caused by blasting vibration during tunnel construction. We compared the measured values with the values predicted by equations of vibration and noise inside and outside of the houses to be preserved.

As a result of our study, we found that the noise level inside the house was often larger than just outside the house. The difference between the noise inside the house and that in field can theoretically differ by 10 dB at maximum. When the noise problem in the tunnel excavation is discussed, this result indicates that not only air propagation but also the solid-borne sound should be considered. If the sound measurement in the field is employed as the reference, we need to use control values at least 15 dB lower than the conventional control value.

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