Master's lecture in Mechanical Engineering - Katrín Helga Ágústsdóttir

Master's student: Katrín Helga Ágústsdóttir

Title: The design of slushflow barriers:  Laboratory experiments

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Faculty:  Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

Advisor:  Halldór Pálsson, Professor at the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

Other members of the masters committee:

Ásdís Helgadóttir, Assistant Professor at the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

Kristín Martha Hákonardóttir, Civil Engineer at Verkís

Tómas Jóhannesson, Coordinator of Glaciological Research at the Icelandic Meteorological Office

Examiner: Vigfús Arnar Jósefsson,Engineer at Verkís

Abstract

Snow avalanches and slushflows have endangered Icelanders since the settlement, particularly in the northern-, eastern- and north-western part of Iceland, and have cost many human lives. While snow avalanches are usually the main threat, some villages in the north-west are threatened by slushflows as well and protection measures for these villages must be designed to provide protection against both snow avalanches and slushflows. Slushflows are a saturated mixture of snow and water. Granular flows such as snow avalanches are compressible, while slushflows are more like waterflows and nearly incompressible. The aim of this thesis is to identify an engineering design that can effectively stop slushflows upstream of a catching dam. Experiments were carried out in a laboratory set-up, using water flowing down an inclined chute to simulate the behaviour of slushflows hitting different types of obstructions. The experiment tested different upstream angles of impermeable dams both with and without braking mounds. Also tested were few a boulder barrier designs that are known to function well as breakwaters. Video recordings were made, and the footage used for further analysis and measurements to identify the most effective protection. Results indicate that the most effective solution is a steep boulder barrier with 90° upstream angle with an impermeable back. If such construction is not considered feasible, the second-best design is a impermeable barrier with >75° upstream angle and at least one row of braking mounds. It was, furthermore, found that a dam based on a traditional berm