An investigation of tunnel linings is performed at two tunnels in the US using complimentary noncontact techniques: air-coupled ground penetrating radar (GPR), and a vehicle-mounted scanning system (SPACETEC) that combines laser, visual, and infrared thermography scanning methods. This paper shows that a combination of such techniques can maximize inspection coverage in a comprehensive and efficient manner. Since ground-truth is typically not available in public tunnel field evaluations, the noncontact techniques used are compared with two reliable in-depth contact nondestructive testing methods: ground-coupled GPR and ultrasonic tomography. The noncontact techniques are used to identify and locate the reinforcement mesh, structural steel ribs, internal layer interfaces, shallow delamination, and tile debonding. It is shown that this combination of methods can be used synergistically to provide tunnel owners with a comprehensive and efficient approach for monitoring tunnel lining conditions.
Joshua White and Stefan Hurlebaus — Zachry Department of Civil Engineering, Texas A&M University, 3136 TAMU, College Station, TX 77843, USA; Texas A&M Transportation Institute, Texas A&M University System, 3135 TAMU, College Station, TX 77843, USA
Parisa Shokouhi — Federal Institute for Material Research and Testing (BAM), Unter den Eichen 87, 12205 Berlin, Germany
