충격반향기법을 이용한 터널 내 궤도 하부 상태 평가 기법에 관한 연구

An impact echo test using acoustic waves was performed to evaluate the overbreak filling method for the bottom of the track in the operation line in a tunnel. The test locations were location A, which consisted of a concrete layer at the bottom of the track, and locations B, C, and D, which consisted of gravel layers up to the rock layer under the concrete track layer of a certain thickness. Test results showed that shock waves resonated at specific frequencies and spectral density was amplified at locations B, C and D. In addition, the depth to the gravel layer below the track was calculated from the theoretical value using the frequency at which the maximum spectral density appeared. The reliability of the test was verified through comparison with actual values. This evaluation technique will enable a clear and rapid evaluation of the bottom of the track within operation lines in tunnels.