Automated inspections in tunnels

Cristina G. Pedraz/DICYT Nowadays, inspections in road and rail tunnels are performed manually. One or more technicians regularly walk through infrastructures trying to locate defects and faults, incidents recorded on cards and sometimes with photos or thermal images. In order to use technologies in these inspections automatically and to maintain tunnels preventively, researchers at Cartif (a technological center in Valladolid, Spain) and a company called Geocisa have embarked in the project SITEER.

As DiCYT was told by researchers Fernando Gayubo and David Olmedo, this is an ambitious project in the Innpacto program by the Spanish Ministry of Economy and Competitiveness. With a one million Euros budget, the project will be developed until the end of 2015.

“Nowadays, preservation and maintenance are very important to extend the useful life of all infrastructures, including tunnels, very complex structures. Safety is a key element and we are looking for tools to reduce problems and risks”, they explain.

The project is a response to a need identified: the fact that check activities are performed visually by technicians who need to talk through tunnels, “which makes them unprofitable inspections”. “We are not talking about automated activities, a large amount of information is collected and it is not well organized and difficult to manage, so developing a system to organize data and perform automated inspections will allow to carry out preventive maintenance”, they state.

Consequently, “the task is to understand tunnels’ situation and detect defects and faults” in order to enhance safety in these infrastructures and extend their useful life, “also reducing economic costs, because when performing preventive upkeep, defects can be solved before they get worse and repairs more expensive”.

Thermography and Reflectance

In order to automate this process, researchers are to combine and use two nondestructive techniques: thermography (to measure the temperature of a given surface from a distance by infrared radiation) and reflectance (to estimate the capacity of surfaces to reflect light). “This techniques are not novel, but their combination may solve the problem of tunnel inspections, which is actually novel”, researchers state. These techniques were chosen because their technical feasibility has been proven and their cost is pretty much reasonable. Moreover, researchers in this team are experienced in their use.

The first step toward this direction will be to establish the extent of these technologies to solve inspection problems, individually and jointly. Second, they want to use both technologies in a single terminal, a device “able to effectively classify defects or potential faults in these infrastructures”.

In order to try them, a pilot run will be conducted in a road tunnel; once the device is developed, the main purpose is to use it in a wagon “allowing us to inspect railway tunnels while moving”. In addition, if the system is effective, it may be used to inspect other infrastructures “such as water or gas pipes, in which technology is not being used at the moment.”

Geo-referenced Areas

Another novel aspect of SITEER is that data collected will be geo-referenced, that is, exact coordinates of incidents will be recorded. According to the researchers, this is an enormous advantage because “in an upcoming inspection, a defect can be easily located (a small crack or damp patches, for instance), allowing to observe its evolution, so if it has grown, an intervention can be performed before a greater problem occurs”.

Cartif and Geocisa, based in Madrid (Spain), have been collaborating for several years in various research projects regarding infrastructures and construction.