International Conference Vajont2013 - 8 October

1. A geomorphological reconnaissance of
structurally-controlled landslides in the
Dolomites
Alan P. Dykes
Edward N. Bromhead
S. Mahdi Hosseyni
Maia Ibsen
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School of Civil Engineering and Construction

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
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3. ‘bedding-plane failure’
 often referred to as
‘dip-slope failure’
distinct from...
Harrison and Falcon (1937)
‘bedding-controlled’
landslides, e.g.
Bromhead (1978)
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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)
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5. Google
Earth
view
Coppola and Bromhead (2008)
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6. Cinque Torre
Alleghe
Borta
(Caprizi )
Longarone
Pineda
Vaiont
(East)
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School of Civil Engineering and Construction

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
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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...
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School of Civil Engineering and Construction

9. Cinque Torre
Alleghe
Borta
(Caprizi )
Longarone
Pineda
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10. Tessina
Cinque Torre
Alleghe
Borta
(Caprizi )
Pineda
Vaiont
(East)
Pian Formosa
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11. Nove
Fadalto
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12. Cinque Torre
Alleghe
Longarone
Pelmo
Pontesei
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13. DIP-SLOPE FAILURES
IN THE DOLOMITES
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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
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15. 1. ALLEGHE
planar scar clearly defined
by limestone bedding
permeable dam resulted
from narrow river gorge
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16. 2. BORTE: August
1692
L = 2070 m
H = 1040 m
α = 27° (mean)
32° (upper scar)
overdip slopes along tributaries (?)
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17. 2. BORTE
bedding planes in the
dolostone clearly define
the failure
similar to Alleghe but the
smaller dam breached
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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
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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)
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20. 4. VAIONT: October 1963
East Side
L = 1450 m
H = 800 m
α = 29° (mean)
35° (upper scar)
overdip slope along the gorge
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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)
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School of Civil Engineering and Construction

22. 5. CINQUE TORRE: age unknown
L = 3000 m
H = ~700 m
α = 18° (mean)
30° (upper scar)
underdip slope
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23. 5. CINQUE TORRE
Viero et al. (2010)
suggested failure of
argillaceous rocks
over the Dolomia
Cassiana
Both Figures from Viero et al. (2010)
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24. 5. CINQUE TORRE
strong structural control –
30° dip dominates the site
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25. COMPARISONS WITH A FEW DIPSLOPE LANDSLIDES ELSEWHERE
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26. SAIDMARREH
.5
15
km
failure of 38 km3
occurred on nine
bedding planes in
weak interbedded
limestones and mudstones
Roberts and Evans (2013)
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27. PALLISER
‘rock-bridges’
(Sturzenegger and Stead, 2012)
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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
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School of Civil Engineering and Construction

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
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School of Civil Engineering and Construction

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)
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School of Civil Engineering and Construction

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.
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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.
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School of Civil Engineering and Construction

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.
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School of Civil Engineering and Construction