Tunnel Pressure Changes

Datum Monitoring Services installed six pressure transducers in Wolvercot Tunnel, as part of a internal pressure environment study for Chiltern Railways, Evergreen 3 line upgrade. The purpose of the survey was to measure the effect of pressure changes in Wolvercot tunnel as passenger and freight trains pass through. The tunnel is currently home to a population of Common and Soprano Pipistrelles, Daubenton’s and Natterer's Bats. All Bats are very sensitive to sudden air pressure changes. Barotrauma occurs when they are exposed to changes in air pressure within their immediate vicinity. The sensors were placed at various points throughout the tunnel to measure peak positive and negative pressures for each passenger and freight train. The same sensors were re-positioned in South Harrow Tunnel. The tunnel is both slightly longer and larger in cross section when compared to Wolvercot. The tunnel had both passenger and freight trains passing through at greater speeds. Train direction, speed and crossings in the tunnel were all recorded as part of the survey. Over 3 million data points were successfully recorded over a 2 week period from the instrumentation. Results were considerably less than originally expected.