1. Division of Fluid and Experimental Mechanics, Luleå Univ. of Technology, 971 87 Luleå, Sweden (corresponding author).
2. Division of Mining and Geotechnical Engineering, Luleå Univ. of Technology, 971 87 Luleå, Sweden.
3. Division of Fluid and Experimental Mechanics, Luleå Univ. of Technology, 971 87 Luleå, Sweden.
4. Dept. of Civil and Transport Engineering, Norwegian Univ. of Science and Technology, NO-7491 Trondheim, Norway.