Page 349 - 360.revista de Alta Velocidad - Nº 5

Influence of Aerodynamics in Tunnels Design

6.5 Location of control sections for auscultation

The instrumentation arranged in the tunnel of La Cabrera has been very varied and with very
different objectives.
Due to the intention to evaluate the effect of the sonic boom, two sonometers were installed
in the vicinity of the portals to record the decibels corresponding to each generated pressure
wave, in order to obtain the frequency spectrum of the burst in bands of thirds of octave. The
La Cabrera tunnel presents ideal conditions to measure this effect since, as mentioned, it has
been verified with a field visit that this effect occurs. Sound level sonometers have been placed
50m from the portal of the Valencia side.
As it has been necessary to measure pressure variations and wind speed inside the tunnel,
pressure sensors and triaxial anemometers have been installed.
At the entrance and exit of the tunnel displacement sensors or strain gauges have been installed
to record the passage of trains and to determine the speed, composition and type of train that
circulates.
Likewise, the pressure, air velocity in the longitudinal component, temperature, humidity and
environmental pressure, as well as the passage of the train have been recorded.
The central section of the train has been instrumented with pressure sensors, anemometers and
train passage detectors. This section is located towards the middle of the tunnel and has sought
the proximity to a connecting gallery in the tunnel of La Cabrera, in order to instrument in and
out of the gallery with pressure sensors.

Figure 9. Instrumentation set in La Cabrera Tunnel

To summarize, the scheme of installation of the sensors in the tunnel of La Cabrera was the
following one:
• A sensor to measure pressure, temperature and humidity outside the tunnel at ch 351 + 277
(tunnel entrance) and 358 + 450 (section 3).
• Two sound level meters on the outside of the outlet with the corresponding data acquisition
equipment and separated by one meter and placed at 50m from the portal (section 4).

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 347