Method for the Continuous Observation of Tunnel Leakage

Background and Objectives of the Study

  Water leakage in tunnels can deteriorate concrete and undermine the safety of passing vehicles. In snowy and cold regions such as Hokkaido, water leaks freeze when the temperature drops in winter, causing icicles to form. These are removed by road patrols and other means, but the work is labor-intensive and costly. In addition, the location and amount of water leakage can change with the season and rainfall (Fig. 1), so it may not be possible to accurately determine the location of a leakage during tunnel inspections.

  To solve this issue, the Geological Hazards Research Team developed a method to continuously observe changes in the amount and timing of water leakage from the concrete walls of a tunnel.

Summary of Research Results

  We were able to grasp changes in water leakage in the concrete walls of the tunnel by capturing serial images with a night vision camera. By binarizing the captured images into black and white and assuming that the white parts had a dry wall surface and the black parts had a wet wall surface (Photo 1), we can calculate the area and percentage of water leakage, and capture the short-term (daily) and long-term (monthly) fluctuation in leakage. In addition, changes in the amount of leakage over time can be estimated from the change in leakage area. In winter, we can observe ice from water leakage forming and detaching from the walls again and again. It should be noted, however, that inside the tunnel, warm air flowing in from the outside can cause fog to form and make the entire wall surface moist, making it unsuitable for observing the condition of leakage.

  

(Contact: Geological Hazards Research Team, CERI)