Towards Automating Tunnel Inspections with Optical Remote Sensing Techniques

In this article a new concept and measurement results of a novel system that aims to replace the manual hammering for acoustic delamination detection using a remote sensing approach is presented. A strong, pulsed laser serves as a hammer and creates a plasma induced shockwave on the concrete surface. This shockwave excites characteristic, resonant vibrations if a delamination is present. A second laser is used to remotely detect these vibrations via a coherent measurement technique. In combination with a recently developed laser scanner, which allows the simultaneous measurement of the 3D-geometry and the detection of water on the tunnel surface via a multispectral approach, this novel system meets many requirements of tunnel inspections.