Tunnels Structural Monitoring System

In 2005, the consortium FiberSensing, EPOS - Empresa Subterrânea de Obras Públicas S.A and CEGEO won the tender for the permanent measurement system of the Rossio Tunnel (Lisbon) with the SysTunnel System Solution.

The SysTunnel is a complete tunnel monitoring system that allows the measurement of deformation, convergence and temperature in different sections of the structure using exclusively optical sensors. The installed monitoring system at Rossio Tunnel consisted of 109 instrumented sections with seven strain sensors and one temperature sensor each connected to one single measurement unit.

Strain and temperature sensors installed along the tunnel.

SysTunnel Monitoring System

This System uses one instrumented metallic profile per section with strain and temperature sensors of the weldable type. Each set of sensors is a branch of the global sensing network and is connected to the measurement system through an optical cable.

On this application, the strain sensors, together with the temperature sensor, measure temperature compensated strain in seven known positions of the tunnel cross-section. Metallic profiles materialize the structural unit where the sensors are applied.

1 Measurement Unit + 1 Expansion Multiplexer with 1x128 channels were used to interrogate all sensors

playSensors at Rossio Tunnel

The measurement unit was connected to a REFER server, via Ethernet, where data is continuously being processed and stored.

The System measures the strain of each sensor with a 1με resolution and ±2με accuracy. The system ensures an accuracy of around 1 mm and a resolution of < 10 μm on the displacement values calculated using the MEMCOT method – as patented on the National Institute of Intellectual Property under the number 103 058 -  based on the measured strain and with an initial topographic calibration with 1mm accuracy.

Data Management Software (DMS)

All collected data is being stored and managed with a Data Server Application running on a dedicated server. The application was developed in order to receive process and save the acquired data.

The remote user interface allows registered users to access the database anytime anywhere (to configure, consult and operate the Structural Monitoring System remotely) and the search for results in various combinations. Data can be viewed in graphics and/or spreadsheets and combining different sensors in a great number of ways.


The measurement system should be preferably installed outside the tunnel in a technical rack.

In the Rossio Tunnel, however, the technical rack equipped with UPS to prevent power failures was installed inside the tunnel. A specially designed closet was installed in the owner designated refuge hole. The structure was equipped with thermo-controlled ventilation to prevent overheating, dust filters to reduce the dust on the rack and a strong lock to prevent vandalism and theft.

  • +100 Monitored Sections
  • +800 Installed Sensors
  • 18 km Fiber Optic Cable Network
  • +10 Measured Parameters

The SysTunnel installed on the Rossio Tunnel has been continuously running and collecting data from May 2008. Registered users can remotely collect data through the REFER’s intranet.

Since 2008 and to the present date, only a few incidents were reported: the first one led to the replacement of a UPS system that supported the measurement unit, and a second, which led to the substitution of a sensor.

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