Laboratory investigation of performance of a screen type debris-flow countermeasure

ABSTRACT

Debris-flows are forms of landslides in mountainous regions that can potentially cause significant damage. Structural countermeasures to mitigate an entire debris-flow may become unrealistically massive and expensive. If the flow cannot be stopped completely, one may alternatively consider reducing the impact and velocity of the flow using energy dissipating structures. A debris-flow screen is such a countermeasure designed to dissipate energy. A screen is made by parallel grids, with some gaps, placed in the direction of the debris-flow on an elevated foundation. This structure acts as a filter for separating water from the saturated debris-flow to reduce its flow energy. This paper presents a laboratory model test investigating the effect of the screen with length (0.5 m and 1.0 m) and opening width (2 mm, 4 mm and 6 mm) in dissipating the debris-flow energy. The effectiveness of the screens was determined in terms of reductions in the run-out distance and the flow velocity. The importance of the screen length and the opening width is demonstrated. A hypothesis that the optimum opening size should be close to of the solid material seems to be validated. The application of the laboratory observations to the field is indicated based on the energy line and scaling principles.

KEYWORDS:

• Debris-flow
• debris-flow screen
• countermeasure
• laboratory testing
• physical modelling

Acknowledgements

The Norwegian Public Roads Administration (NPRA) financially supported this study under the E39 ferry-free highway project, and the study was conducted in close cooperation with the Klima2050 project. The authors would like to thank Frank Stæhli and Tage Westrum, for building the screens and the plates, and Geir Tesaker for operating the crane during the experiment.

ORCID

A. L. Yifru http://orcid.org/0000-0002-4091-5286

Additional information

Notes on contributors

A L Yifru

Mr A L Yifru is a Ph.D. candidate at the Department of Civil and Environmental Engineering, Norwegian University of Science and Technology. His research area includes countermeasures for debris- and mud-flow hazards.

E Laache

Ms E Laache is a Geotechnical Engineer and Consultant at Rambøll Norge AS, Kristiansand, Norway. She obtained her M.Sc. in Geotechnical Engineering from the Department of Civil and Environmental Engineering, Norwegian University of Science and Technology. She is now working as a Geotechnical Consultant in projects for infrastructure and buildings in Norway.

H Norem

Prof H Norem is a Professor Emeritus at the Department of Civil and Environmental Engineering, Norwegian University of Science and Technology. His main research is in snow engineering, drifting snow and snow avalanches. He has also presented papers about submarine slides and flow slides.

S Nordal

Prof S Nordal is a Professor in Geotechnical Engineering at the Department of Civil and Environmental Engineering, Norwegian University of Science and Technology. His research interests are computational Geotechnics, particularly in constitutive modeling of soil, numerical modelling for geotechnical design and applications of geomechanical modelling related to Geohazards.

V Thakur

Prof V Thakur is a Professor in Geotechnical Engineering at the Department of Civil and Environmental Engineering, Norwegian University of Science and Technology. His current research activities involve flow slides in sensitive clays, landslides and slope stability, debris flow, soil characterization including sample disturbances/storage effect, strain localization, unsaturated soil mechanics, geo-environmental engineering, ground stabilization methods, e-learning in geotechnical engineering, finite element modelling, analytical modelling and physical modelling.