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

Determining the thickness of concrete lining and detecting of the cavity where is located behind tunnel lining plays an important role in the safety diagnosis of tunnel structure and the quality control during the construction. In this study, we made use of Impact-Echo method with single-axis and triaxial accelerometer in order to find the cavity or flaw. The thickness estimated by this method was good agreement with the thickness of concrete plate model. According to the use of single and multi-component accelerometer, we studied the characteristic of power spectrum and phase angle in frequency domain and examined the accuracy of the estimated thickness. In the field application, the method can clearly show the location and depth of the cavity in the reinforced concrete lining of subway tunnel.