Effects of Acoustic Waves on Buried Tunnel Structures Under an Impact Load

In this paper, the transmission and reflection of acoustic waves into and from an underground tunnel are investigated by producing an impact load on the ground and measuring the acoustic pressure levels at different time intervals. For this purpose, a sound detector is placed on the ground and then from an arbitrary location on the surface, acoustic waves are transmitted into the ground from an acoustic source. The pressure levels of acoustic waves transmitted into the tunnel space and reflected back to the ground surface are measured, and the effects of several parameters on the attenuation of acoustic pressure levels of transmitted and reflected sound waves are evaluated. Moreover, the effects of parameters such as soil type, concrete type and thickness, buried depth of the underground structure and also the effect of acoustic absorbers on the transmission, propagation and reflection of acoustic waves into and from the tunnel are investigated. The results obtained indicate that the two parameters of soil type and buried depth have the greatest effect on the transmission of acoustic waves, whereas all the parameters considered are important with regard to the reflection of acoustic waves. In addition, it was observed that the use of acoustic absorbers in tunnel structures has a significant effect on the attenuation of transmitted and reflected acoustic waves.