Model testing of the drainage screen type debris flow breaker
MetadataVis full innførsel
- Avhandlinger 
Debris flows are a hazardous geological phenomenon that occur in regions with steep mountainous terrain that has at least occasional rainfall. The poor predictability combined with characteristics as high flow velocity, high impact forces and long runout, makes debris flows one of the most hazardous landslide types. Their great destructive powers may cause loss of human lives, damage to communities, agriculture and infrastructure which all may have great direct or indirect costs. This master thesis gives an introduction to debris flows, debris flow countermeasures and the drainage screen type debris flow breaker. The drainage screen type debris flow breaker has only been studied in Japan where they named it debris flow breaker. Physical experiments are done to investigate the process and physics of debris flows and to evaluate the drainage screen type breaker as a countermeasure. Parameters studied are length, opening width and percentage opening. The effectiveness of the countermeasure is determined by the reduced runout compared to tests where there are no countermeasures in the physical model. A total of 27 tests were carried out and 6 different drainage screen type breakers were tested. 6 tests were also done on solid plates to see the effect of the breaker structure going horizontally out of the slope instead of being integrated into the slope. The main findings were: - The values observed for the debris flow front velocity, flow height and slope of the energy line for the reference tests were within the normal values of a real debris flow - The interaction between the drainage screen type breaker and the debris flow appeared to be as the theorysuggested. Water drained through the opening widths and the debris flow front or body stopped on top of the drainage screen depending on the length of the screen. - The most effective drainage screen was 1.0 m long and had 2 mm opening widths. This breaker had a 76% effectiveness where the effectiveness is measures in terms of reduced runout compared to the reference tests. - All of the 1.0 m long drainage screens were more effective than the 0.5 m long screens, regardless of the opening width. - The effectiveness of the 1.0 m long drainage screen was also better than all previously tested debris flow countermeasures which included check dams, slit dams and baffles. - The results from the physical modeling of the drainage screen type debris flow breaker indicated that this type of breaker is an effective countermeasure that could be trusted and used.
Master thesis - NTNU Trondheim - Norwegian University of Science and Technology. Department of Civil and Transport Engineering.