Application of FCTEM60-1 Instrument in Invert Rebar Testing for Highway Tunnel

The invert of a highway tunnel is the foundation for the entire tunnel structure. Its quality has a direct influence on the stability of tunnel structure. However, in practice the tunnel invert has various defects for a variety of reasons. FCTEM60-1 instrument is able to rapidly cut off the current using constant voltage clamping technique, thus significantly reducing the shallow dead-zone effect of transient electromagnetic (TEM). In this study the instrument is applied to testing invert rebar execution in a highway tunnel. The study result shows FCTEM60-1 instrument successfully detected the invert rebar, demonstrating its feasibility and reference value to tunnel quality test.