Hermanns - understanding long term slope

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International Conference Vajont2013 - 8 October

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  • Reginald
  • Reginald
  • Hermanns - understanding long term slope

    1. 1. Understanding long-term slope deformation for stability assessment of rock slopes: The case of the Oppstadhornet rockslide, Norway Reginald L. Hermanns Thierry Oppikofer, Halgeir Dahle, Trond Eiken, Susan Ivy-Ochs, Lars Harald Blikra Vajont conference, Padova, October 8th -10th, 2013
    2. 2. Content • Characterisation of fjord lands • Systematic mapping program for unstable rock slopes in Norway • Oppstadhornet rockslide in western Norway • Unstable rock slopes and deglaciation in Norway
    3. 3. Characterisation of fjord lands
    4. 4. The challenge:
    5. 5. 1947 today Tjelle, 1756
    6. 6. Characterisation of fjord lands Tafjord 1934
    7. 7. Characterisation of fjord lands
    8. 8. Certain fjellskred events Name Tjelle Tafjordulykka Skafjellet Lausneset Loenulykke 1 Loenulykke 3 Pollfjellet County Møre og Romsdal Møre og Romsdal Møre og Romsdal Møre og Romsdal Sogn og Fjordane Sogn og Fjordane Troms Municipality Nesset Norddal Stranda Stranda Stryn Stryn Lyngen Year 1756 1934 1731 1300 1905 1936 1810 Municipality Sande Stranda Stranda Norddal Gaular Årdal Year 1700 1749 1938 1811 1786 1983 Volume Displaceme [Mm3] Lives nt wave 15.0 32 Yes 3.0 40 Yes 6.0 17 Yes 0 Yes 0.4 61 Yes 1.0 74 Yes 14 Yes Uncertain fjellskred events Name Storefonna Geirangerfjorden Skafjellet Arnafjord Hestadfjorden Årdalsfjorden County Møre og Romsdal Møre og Romsdal Møre og Romsdal Sogn og Fjordane Sogn og Fjordane Sogn og Fjordane Volume [Mm3] 0.1 0.4 0.2 Lives 0 0 0 45 0 0 Displaceme nt wave Yes Yes Yes Yes Yes Yes
    9. 9. Systematic mapping program for unstable rock slopes in Norway Tafjord 1934 Assumption: • Slow deformation indicating slope instability • Acceleration phase prior to collapse
    10. 10. Systematic mapping program for unstable rock slopes in Norway Task: • • • • Tafjord 1934 Find all unstable rock slopes which may collapse catastrophically Understand geologic condition of each unstable slope Rank all slopes based upon their hazard and risk 24/7 monitoring and early warning Mapping approach: • Risk based
    11. 11. Mapping of unstable rock slopes in Norway
    12. 12. Systematic mapping program for unstable rock slopes in Norway
    13. 13. Systematic mapping program for unstable rock slopes in Norway
    14. 14. Oppstadhornet rockslide in western Norway
    15. 15. Oppstadhornet rockslide in western Norway After Braathen et al., 2004
    16. 16. Oppstadhornet rockslide in western Norway After Braathen et al., 2004
    17. 17. Oppstadhornet rockslide in western Norway Bhasin and Kaynia, 2004
    18. 18. Oppstadhornet rockslide in western Norway
    19. 19. Oppstadhornet rockslide in western Norway 10Be exposure age 4.50 m 4 5 6600 4.00 m 3200 a 0.1 mm/a 2.05 m 10300 2.20 m 1.1 3 0.4 mm/a 2.10 m 1.6 2 1700 a 2.2 mm/a 12500 2.85 m 3.2 1 700 a
    20. 20. Oppstadhornet rockslide in western Norway 10Be exposure age Slip rate 2.10 m 3 2.05 m 10300 2.20 m 4 5 6600 4.00 m 2.2 mm/a 2 1700 a 3.2 1 12500 2.85 m 3200 a 700 a Start of sliding: 14.2 ka ago (16.6 ka) 4.50 m
    21. 21. Why did the Oppstadhornet slope did not failed during a seismic event in the geological history?
    22. 22. Understand geologic condition of each unstable slope / Rank all slopes based on their hazard and risk
    23. 23. Understand geologic condition of each unstable slope / Rank all slopes based on their hazard and risk
    24. 24. Unstable rock slopes and deglaciation in Norway 12.8 13.7
    25. 25. Oppstadhornet rockslide in western Norway 12.8 13.7 Start of sliding: 10 ka ago Hermanns et al. 2012
    26. 26. Conclusion • In fjord lands is the area of impact of rock slides often larger than in normal mountain settings • Norwegian fjord land is densely settled and systematic mapping is necessary in order to be able to prepare for future events • Oppstadhornet rockslide is a typical rockslide in western Norway that has large consequences • Oppstadhornet has moved constantly with low rate and is still moving • Movement started 14 ka ago when the top came out of the ice • Other landslides have been moving since the location melted out of the ice sheet with low rate • Long term slip rates are important information to detect acceleration
    27. 27. Thank you for your attention Reginald.Hermanns@NGU.NO

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