Development of in-situ tunnesl-ahead detection system using electromagnetic

ABSTRACT: During tunnel construction, ground failures are often reported due to occurrence of weak zones such as faults, joints, and cavities. By using conventional geophysical characterization methods, it is hard to detect detailed weak rock and fault zone which can lead underground structure to fail after excavation and before supporting. In this study, an enhanced detection system of predicting weak zones ahead of tunnel face is developed for making up the problems of the conventional characterization methods. Using the developed system, case studies are performed for detection of a spherical shaped weak zone and an oriented fault. The experimental results show that the presence of weak zones and their sizes, location, and states can be accurately predicted from electrical resistance measurements through a proper inversion process.