Theoretical and Experimental Investigation of Vehicle-Mounted Transient Electromagnetic Method Detection for Internal Defects of Operational Tunnels

With the durable operation of high-speed railway tunnels in China, many tunnel defects successively appeared in the tunnel lining structure and gradually threatened the safe operation of the tunnels. In the limited maintenance time of high-speed railways, it is urgent to find out and maintain tunnel defects, especially internal defects. We propose an applied detection technology called the vehicle-mounted transient electromagnetic method (TEM). The detection technology aims to rapidly detect and locate the internal defects of the lining structure throughout the entire tunnel. Firstly, we investigate tunnel defects in detail and introduce the rapid detection method. Secondly, we analyze the principle and process of vehicle-mounted TEM. Thirdly, the rationality and applicability of vehicle-mounted TEM are verified by three different methods, including theoretical analysis, numerical simulation, and laboratory experiment. Finally, we compare the inversion results of experimental data under the two conditions. The results illustrate that tunnel surface defects are the external manifestations and characteristics of tunnel defects, while the forms of surface defects are directly related to internal defects. This detection method is suitable for the significant resistivity difference between tunnel defects and surrounding rocks, and its rationality is effectively validated. Furthermore, the apparent resistivity results reveal that there is a low resistivity region in front of the transmitter coil, and that the relative position can be preliminarily judged. The research results can provide a potential and significant application technology for the rapid detection of tunnel defects