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The fiber optic cable lands at Charles De Gaulle Airport in Paris.

During the transit of airplanes, the conditions of the infrastructures are crucial. Aeronautical pavements can consist of large concrete slabs that rise and fall depending on the temperature and weather conditions. Perhaps only a few millimeters, but the continuous passage of airplanes causes a progressive degradation of the pavement.

Charles De Gaulle Airport in Paris, the second busiest in Europe, has therefore initiated an experimental study to analyze the stresses that occur on airport pavement. They have asked NTSG Italy ( Group) to create a monitoring project for the slabs to understand the variations that the structure undergoes over time and consequently understand its health.

The goal is to accurately plan maintenance activities based on the actual conditions of the runway and improve the understanding of the stresses suffered by the slabs to refine the theoretical models used for pavement design

PHASE 1 – structural monitoring of “SLABS”

Some of the airport pavements are made up of different layers of material. The top layer consists of Slabs: 5×5 m cement blocks with a thickness of about 60 cm.

The project involves the installation of fiber optic sensors inside the Slabs on a section of airport pavement, during the pavement construction phase.

In these Slabs, there are iron towers where we have installed MS (strain) and MST (strain and temperature) sensors, humidity sensors, and thermal sensors.

Once the sensors are installed on the towers, the cement casting that constitutes the Slab is carried out, creating a single block: in this way, we can monitor the deformations of the cement due to thermal phenomena and vehicle passage.

In the center of some Slabs, a humidity sensor has been installed to monitor the percentage inside the cement. Furthermore, triplets of thermal sensors are provided on the thickness of the Slabs to measure the thermal gradient and verify the temperature variation within them.

Nello strato di asfalto drenante sottostante le Dalle, sono stati installati dei PIEZOMETRI per verificare l’eventuale presenza di infiltrazioni di acqua.

Another area of experimentation is the analysis of the relative movement of Adjacent Slabs induced by external stresses (aircraft/vehicle transit).

For this purpose, the joints between adjacent Slabs have been sensorized.”

PHASE 2 – Recognition of transit vehicles
Experimental Application

In this case, out target is to trace a portion of the trajectory of the aircraft in transit to characterize their lateral movement on the infrastructure.

To install the sensors, a trench is excavated in the concrete, 2.5 cm wide and 5 cm deep, where the optical fibers are positioned, supported by interlocking supports to maintain all the fibers at the same height

On the same runway, GFRP (strain) sensors and 4 temperature sensors will be installed at the edges.

The installed sensors are as follows:

  • 216 Sensors for deformation distributed on 6 slabs: for each slab, 2 layers of 9 pairs of deformation sensors in an ‘L’ configuration have been installed.
    The ‘L’ configuration consists of two sensors in orthogonal directions at 9 specific points for each slab (at the corners, at the center of each side, and at the center).
    Having the 9 ‘L’s on two levels (upper and lower) per slab (i.e., 18 ‘L’s x 2, totaling 36 sensors per slab) allows for a comprehensive reconstruction of slab deformations.

  • 36 temperature sensors distributed over 6 slabs: for each slab, 2 sets of 3 temperature sensors have been installed (1 per level at two different points per slab), allowing for the evaluation of… thermal gradient on two vertical sections and to compensate for the stress measurements mentioned above.
  • 6 sensors for deformation and temperature (3 pairs of 2) placed between two slabs (2 sensors between slabs 6 and 7, 2 sensors between slabs 2 and 7, 2 sensors between slabs 7 and 8) that allow for the assessment of load transfer between 3 pairs of 2 slabs.
  • 2 humidity sensors in the concrete of the slabs.
  • 2 piezometric sensors to assess the water content in the draining asphalt
  • 10 GFRP rods (arranged in two lines, hence 5 rods x 2) containing a total of 240 deformation sensors. Installed in two trenches transverse to the runway: the deformation sensors in this configuration are triggered by the passage of the aircraft, and the analysis of the product’s data allows for the application of scanning (detection of the aircraft’s pattern as it passes).
  • 4 temperature sensors at the edge of the runway corresponding to the GFRP, for the compensation of stress measurements from GFRP.

Innovative Monitoring System Design: Key Metrics and Sizing

  • 506 Installed Sensors
  • 2400 Meters of Fiber
  • Acquisition Frequency: 1000Hz

The application fields
of the fiber optic sensing monitoring system