Luxembourg Airport Rebuilds Runway with Trimble 3D Machine Control

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The Luxembourg Airport, located in Findel, is a major cargo destination in Europe. Along with ever growing passenger traffic, the airport’s one runway is 4.000 m long and 60 m wide—and was in need of complete renovation and repair after 30 years of operation in order for it to meet international standards.

Airport operators needed a way to complete the runway reprofile without disrupting daily scheduled take-offs and landings. With an eye on speed, flexibility and quality, the operators opted to essentially build a new runway with different asphalt layers over the existing one. The idea was that milling machine  would rectify the profile of the track while the asphalt pavers would apply the asphalt necessary to reach the desired level each night, reopening each morning for normal airport operations to resume.

It’s a high-precision, highly complex mission with no room for delays—but it worked out. The operation was made
possible thanks to a skilled team, 3D machine guidance, state-of-the-art technology from Trimble and the support and training provided by SITECH France, the local Trimble distributor.

Tight schedule
At the outset of the project, the airport granted the construction companies a night slot from 11 p.m. to 6 a.m. to carry out the runway reprofiling project over 210-220 nights divided into two campaigns, in 2021 and 2022.

The Findel Airport Consortium made of Colas, Felix Giorgetti, Karp-Kneip Constructions and JDC Airports based their strategy on 3D guidance for milling and asphalt laying operations.

“Karp-Kneip believes in the benefits of our technology,” explains Norbert Mattivi, business development manager for Trimble civil construction. “As a user of guidance systems for its excavators, graders and bulldozers, the Luxembourg-based company has also adopted Trimble’s 3D machine control solutions for its milling subsidiary Rabotech, which supplies the site’s machines with Colas.”

“It was not possible to carry out this project without 3D machine control, with a classic workflow,” adds Christophe Latteur, head of the Karp-Kneip surveying department. “We knew Trimble equipment and how it worked.”

“And we had tested its reliability,” adds Clément Larher, project director for Colas Projects. On this occasion Colas bought a kit for a milling machine.

SITECH France was also present, not only to install, but also as advisor to assist in the planning and optimal use of 3D systems in this particularly demanding context, with the simultaneous operation of an unusual number of machines.

“We had to train the new operators and be on site for the first two to three night operations, until everything was optimal,” said Damien Grosjean, application engineer at SITECH France.

High precision targets
The runway project began with the creation of a digital project based on a survey of the existing situation by a subcontractor, with a point cloud scanned by mobile mapping. Based on this data and the desired profile, the digital project makes it possible to edit the detailed daily work program.

Next, the construction team equips milling machines and asphalt pavers with 3D machine control systems. This system consists of a Trimble CB460 Control Box and MT900 Machine Targets. There are two to four Wirtgen W200 and W210Fi milling machines and up to 8 Vögele Super 1800-3 and Super 2100-3 pavers mobilized every night for the repair of the runway. More than 16 Trimble SPS930 Universal Total Stations are used for guidance and control of the work performed.

“Our total stations are equipped with a very high precision CDD sensor. The signal emitted by the SPS930 and reflected by the target gives an altimetry accuracy of 1 mm at 200 m,” said Mattivi.

The total stations transmit the position of the prisms in x,y,z coordinates ten times per second to the CB460 Control Boxes via radio. In addition to this system, there are Trimble TCS3 and TCS7 Controllers for setting up total stations, and for checking the level of the milled and paved surfaces. The entire operation requires more than 240 people and over 100 machines and trucks to complete.

Ready, Set, Go
Every night, at 11 p.m., the total stations are set up to control and guide the machines.

“The most impressive thing is this rush, at the sound of the horn, every evening at 11 p.m.,” explains Larher. “Everyone knows where he has to go, how he has to get there and what he has to do.”

The first operation is the pairing of equipment and these total stations. “Each MT900 emits a coded unique LED signal picked up by the total station responsible for tracking this target,” said Mattivi.

“This is one of the advantages of the Trimble system,” explains Latteur. “Each station follows only one prism, and finds it, even if a truck passes between the two.”

In addition, the total stations are positioned behind the pavers and on tripods 3 m high to avoid any interruption of the beam by the compactors at work.

Active tracking technology
The areas to be milled—about 2 m wide depending on drum width—are marked each evening by the TinyRobots, an autonomous line pre-marking solution, equipped with a Trimble SPS986 GNSS Smart Antenna.

The milling machines guided by the Trimble PCS900 Paving Control System can then come into play. “Then we treat the sides of the first zone to cover the entire width of the track,” explains Larher.

“These machines have a single mast carrying the MT900 prism,” says Mattivi. “We thus have an altimetry point which, combined with a Trimble GS420 Machine Control Sensor, allows a milling precision of ± 3mm for work up to 25 m/min.”

Then, after sweeping and application of the bonding emulsion, crews can lay the asphalt. However, this operation is only triggered after surveying, as progress is made, of the milled depths.

Work as groups
The pavers work in groups. The first, guided in 3D on both sides, works to the left of the axis of the track, and gives the level and the slope over a width of 10 m. The second, also equipped with a 10 m screed, works on the right, taking its reference from the left with a sonic on the layer placed by the first. On the right, it is guided by 3D. This pattern continues until crews have covered the entire width of the track. At the end of the project, ramps are made according to international standards for airport runways (1% maximum).

“We apply between two and seven layers of asphalt, 4.5 cm thick, for the wearing course at a maximum of 10 cm,” specifies Larher. “The amount depends on the areas and the gap between the old profile and the target profile. At most, we will have laid 37 cm of asphalt.”

Every night, crews complete from 150 m to 300 m of new surface.
 
A chain of trucks
The supply of asphalt for the pavers is provided by two plants close to the site—and presents some complexity to the logistics as well.

"In fact, in the time slot allocated to us, the milling is finished around 1:30 a.m., there are 2:30 hours left to lay the asphalt and compact it, because it takes two hours for the asphalt to cool down from 160° C at the time of application to 60°C, the maximum allowable for the reopening of the track,” specifies Larher.

On average, 2.500 tons of asphalt are laid per night—equivalent to 60 to 65 trucks, not counting those that remove the milled material from the milling machines, continues the project director. “Not all trucks have time to return to the asphalt plant. Trucks average 1,6 laps,” he adds.

“That’s another advantage of having a 3D model,” adds Mattivi. “Not only for accurately meeting specifications of the project, but also for calculating the necessary quantities of asphalt to be produced, transported and applied each night.”

“When we leave the runway, to make way for the first cargo planes to land, it’s as if we had never been there. But the equipment is ready for work the next night,” concludes Latteur.

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