Dykes - geomorphological reconnaissance

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International Conference Vajont2013 - 8 October

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Dykes - geomorphological reconnaissance

  1. 1. A geomorphological reconnaissance of structurally-controlled landslides in the Dolomites Alan P. Dykes Edward N. Bromhead S. Mahdi Hosseyni Maia Ibsen www.bing.com/maps 12:12:24 School of Civil Engineering and Construction
  2. 2. part of the failure surface of the East side of the Vaiont landslide OUTLINE 1. Introduction 2. Context – the Dolomites 3. Dip-slope failures 4. Comments on landslide characteristics 5. Conclusions 12:12:25 School of Civil Engineering and Construction
  3. 3. ‘bedding-plane failure’  often referred to as ‘dip-slope failure’ distinct from... Harrison and Falcon (1937) ‘bedding-controlled’ landslides, e.g. Bromhead (1978) 12:12:26 School of Civil Engineering and Construction
  4. 4. dip-slope failures controlled by bedding plane geometry with respect to topographic slope: these give rise to dip-slope failures (Cruden, 2000) Geertsema and Cruden (2009) 12:12:26 School of Civil Engineering and Construction
  5. 5. Google Earth view Coppola and Bromhead (2008) 12:12:26 School of Civil Engineering and Construction
  6. 6. Cinque Torre Alleghe Borta (Caprizi ) Longarone Pineda Vaiont (East) 12:12:27 School of Civil Engineering and Construction
  7. 7. Cinque Torre Alleghe Borta (Caprizi ) Longarone Pineda Vaiont (East) maximum elevations decrease eastwards from >3000 m to <2000 m local relief typically 1200–1600 m in the study area most sites involve limestones/dolomites of the Upper Triassic Dolomia Principale 12:12:27 School of Civil Engineering and Construction
  8. 8. Cinque Torre Alleghe Borta (Caprizi ) Longarone Pineda Vaiont (East) complex tectonic history with uplift of up to 6–7 mm y –1 due to ongoing N–S compression landscape shaped by Quaternary glaciation followed by vigorous fluvial processes and mass movements... 12:12:27 School of Civil Engineering and Construction
  9. 9. Cinque Torre Alleghe Borta (Caprizi ) Longarone Pineda 12:12:27 School of Civil Engineering and Construction
  10. 10. Tessina Cinque Torre Alleghe Borta (Caprizi ) Pineda Vaiont (East) Pian Formosa 12:12:24 School of Civil Engineering and Construction
  11. 11. Nove Fadalto 12:12:25 School of Civil Engineering and Construction
  12. 12. Cinque Torre Alleghe Longarone Pelmo Pontesei 12:12:26 School of Civil Engineering and Construction
  13. 13. DIP-SLOPE FAILURES IN THE DOLOMITES 12:12:27 School of Civil Engineering and Construction
  14. 14. 1. ALLEGHE: January 1771 then later in 1771 (smaller) L = 1500 m H = 880 m α = 30° (mean) 31° (upper scar) overdip slope adjacent to river www.bing.com/maps 12:12:27 School of Civil Engineering and Construction
  15. 15. 1. ALLEGHE planar scar clearly defined by limestone bedding permeable dam resulted from narrow river gorge 12:12:27 School of Civil Engineering and Construction
  16. 16. 2. BORTE: August 1692 L = 2070 m H = 1040 m α = 27° (mean) 32° (upper scar) overdip slopes along tributaries (?) www.bing.com/maps 12:12:28 School of Civil Engineering and Construction
  17. 17. 2. BORTE bedding planes in the dolostone clearly define the failure similar to Alleghe but the smaller dam breached 12:12:29 School of Civil Engineering and Construction
  18. 18. 3. PINEDA: age unknown L = 2220 m H = 1130 m α = 27° (mean) 25° (upper scar) mostly dip slope but underdip in the lower part www.bing.com/maps 12:12:30 School of Civil Engineering and Construction
  19. 19. 3. PINEDA failure along the bedding between the Igne and Soverzene Formations (or within the latter unit) Besio and Semenza, in Riva et al. (2009) 12:12:24 School of Civil Engineering and Construction
  20. 20. 4. VAIONT: October 1963 East Side L = 1450 m H = 800 m α = 29° (mean) 35° (upper scar) overdip slope along the gorge www.bing.com/maps 12:12:29 School of Civil Engineering and Construction
  21. 21. 4. VAIONT dip-slope failure of somewhat deformed thin beds of limestone vis ible fa i lur e su rfa c e inter pola ted failu re s urfa ce cross-section along N15°W (approx. centre of East side) 12:12:29 School of Civil Engineering and Construction
  22. 22. 5. CINQUE TORRE: age unknown L = 3000 m H = ~700 m α = 18° (mean) 30° (upper scar) underdip slope www.bing.com/maps 12:12:30 School of Civil Engineering and Construction
  23. 23. 5. CINQUE TORRE Viero et al. (2010) suggested failure of argillaceous rocks over the Dolomia Cassiana Both Figures from Viero et al. (2010) 12:12:31 School of Civil Engineering and Construction
  24. 24. 5. CINQUE TORRE strong structural control – 30° dip dominates the site www.bing.com/maps 12:12:31 School of Civil Engineering and Construction
  25. 25. COMPARISONS WITH A FEW DIPSLOPE LANDSLIDES ELSEWHERE 12:12:33 School of Civil Engineering and Construction
  26. 26. SAIDMARREH .5 15 km failure of 38 km3 occurred on nine bedding planes in weak interbedded limestones and mudstones Roberts and Evans (2013) 12:12:33 School of Civil Engineering and Construction
  27. 27. PALLISER ‘rock-bridges’ (Sturzenegger and Stead, 2012) 12:12:33 School of Civil Engineering and Construction
  28. 28. 20–25° 45° 26° 27° Flims, Switzerland Saidmarreh, Iran Pineda Borta 29° Alleghe Vaiont (East) Cinque Torre 42° Palliser, Canada (latest slide) Montclús, Spain 12:12:24 School of Civil Engineering and Construction
  29. 29. 20–25° 26° Saidmarreh, Iran 25° Pineda Borta up p er sc ar g rad ien t 45° Flims, Switzerland 35° Alleghe Vaiont (East) Cinque Torre 42° Palliser, Canada (latest slide) Montclús, Spain 12:12:24 School of Civil Engineering and Construction
  30. 30. 20–25° 25° Pineda Borta 35° Flims, Switzerland Ekström and Stark (2013)  height drop and rupture depth scale with length of failure Alleghe Vaiont (East) Cinque Torre 42° Palliser, Canada (latest slide) 12:12:24 School of Civil Engineering and Construction
  31. 31. 20–25° 25° Pineda Borta 35° Alleghe Vaiont (East) Cinque Torre 42° Palliser, Canada (latest slide) Flims, Switzerland We interpret our extremely limited data as follows: (a) as size (length) increases, the area of failure surface controlled by higher strength probably reduces; (b) as size reduces, a steeper slope is needed for shear stress to exceed available strength. 12:12:25 School of Civil Engineering and Construction
  32. 32. CONCLUSIONS 1. Failure along the bedding is probably as common in the Dolomites as it is in any mountain region dominated by strong but tectonically deformed sedimentary rocks (particularly carbonates) 2. We make no assumptions about the western half of the Vaiont landslide, but we suggest that there appears to be nothing inherently surprising about the East side failure, which appears to be typical of the dip-slope failures of the southeast Dolomites region. 12:12:25 School of Civil Engineering and Construction
  33. 33. ACKNOWLEDGEMENTS Stefano Devoto, Emanuele Forte and Fulvio Podda (all Trieste University) assisted APD with fieldwork at Vaiont in September 2012 and provided additional information about other sites. 12:12:25 School of Civil Engineering and Construction

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