Identification and monitoring of subsurface structure of tunnel using electromagnetic method

Abstract

Since ITB-Saraga tunnel was built in 1997, there was no such a monitoring ever took to investigate the internal structure. In contrast, the information of internal structure is needed to identify the self-defect of tunnel caused by the active traffic on the upside of tunnel. The aim of this survey is to identify and monitor the internal structure of ITB-Saraga tunnel using Ground Penetrating Radar (GPR). GPR is chosen because it can detect defects of tunnel using electromagnetic wave which is showed in the existence of contrast anomalies of magnetic permeability, dielectric constant, and resistivity. To fulfil the requirements, acquisition along the surface, processing and interpretation data, and analyzing the results are necessary. The 100 MHz antenna is chosen from forward modeling, and sampling rate value is 850 MHz with trace interval 0.1 meter. The data then is processed with ReflexW software. The result is radargrams that shows the upper structure of the tunnel (0−8.5 meters), and further analysis could give more detailed structures, even the self-defect tunnel itself. The results can be used as additional information to minimize the casualties if disaster occurs.