Inspection of tunnel lining of the Madrid-Sevilla AVE railway through georadar

The Madrid-Sevilla AVE railway has been working since 1992. In its layout there are 17 tunnels with a variable length between 300 and 2,500 meters. All these tunnels have a massive concrete lining with metallic reinforcement in some sections. The high circulation speed of trains in this line makes it necessary for all its facilities to comply with extremely rigorous specifications, and this obliges to the implementation of a watchfulness and maintenance plan for them. In this plan, the inspeetion of the tunnellining is included. The tunnel inspeetion program started in 1995 and includes the auscultation, both visual and using geophysical techniques, the perforation of slim bores and the observation through boroscopio. The fundamental part of this inspection is carried out through the Georadar geophysical technique with the specific aim of identifying pos sibie voids in the concrete lining. As a secondary objective, the possible variations in the lining thickness are studied.