Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Detection of the cavity behind the tunnel lining and estimation of structure thickness are of critical importance for the safety diagnosis in the tunnel maintenance and the quality control during the construction. In this study, we made use of Impact-Echo method in concrete slab model with single-axis accelerometer in order to estimate the thickness and find the cavity or flaw. Impact-Echo signals were processed by the conventional method, based on Fourier transform, and the time-frequency analysis which depends upon wavelet transform. We demonstrate that the wavelet transform separates Impact-Echo signals from noise. The time-frequency analysis using wavelet transform is able to clearly discriminate between response of the cavity or the delaminated slab and the perfect bond area. The proposed method provides us with a robust and powerful tool for interpretation of Impact-Echo signals.