Comparison of Detection Effect of Cavities Behind Shield Tunnel Segment Using Transient Electromagnetic Radar and Ground Penetration Radar

Nowadays, evaluation of cavities behind shield lining segment is still a problem in the engineering inspection field. In order to make up the limitation of the traditional inspection method which is the transient electromagnetic method (TEM) and the ground penetration radar method (GPR). In this paper, a new detection technique is proposed, based on the principle of the TEM, a self-developed product, transient electromagnetic radar (TER) is applied for the research of the evaluation of cavities behind shield tunnel lining segment. The feasibility of cavities detection using TER is proved by designed modeling test, the pattern of resistivity changes during the test are summarized for distinguishing different contact status behind the tunnel segment. Meanwhile, a constructed shield tunnel is used for the field test to comparing the application effect between 900 MHz antenna GPR and TER. Through analysis test images and abnormal signals measured by TER and GPR, and verified by drilling tests, results show that TER has much clearer images than GPR in interpretation data. Development of the TER technique gives engineers a new solution for the detection of cavities behind the segment and has wide application prospects.