STABILITY AND MOTION ANALYSIS
OF THE VAIONT SLIDE
University of British Columbia, Canada
Old technology: Method of Slices
1) Work out the equilibrium of each slice
2) Calculate the equilibrium of the slice assembly
3) Results depend on assumptions regarding the
interslice force X (mobilization of internal strength)
Data: Selli and Trevisan (1964)
E. Semenza (1960)
Semenza sections plus sliding surface reconstruction
(Hendron and Patton, 1984)
2D LE analysis
MP Factors of Safety
(Hoek et al., 1997)
F=0.48 to 0.66
F=0.70 to 0.86
Conclusions – 1) highly asymmetric case,
2) internal strength increases F by 0 to 50%,
depending on cohesion and shape.
3D Analysis, Method of Columns (Hungr et al., 1989)
294 million m3
Distribution of strength. Optimize sliding direction.
Single stage, Volume = 323 million m3 (including water)
Conclusions – 1) direction optimization is
necessary, 2) Constraint (with cohesion) is needed
3D flexible block
model (Aaron, 2013)
1) Differential movement
of columns is
permitted in the
vertical direction but
not in the horizontal
2) No shear stress on
Sliding mass displacement:
ϕ=23º on bedding, plus cohesive
constraint, piezometric surface
Real (after slide)
Water displacement: V MAX = 10 m/s
Water displacement: V MAX = 20 m/s
1) Landslide was highly asymmetric
2) Internal strength contributed to the stability of typical
sections, to a limited extent
3) The structural constraint on the right flank was
4) Cohesion of the intact rock mass played an
important role, but is difficult to quantify
5) The speed of the landslide is not difficult to explain
and was due largely to the loss of cohesion in the
interior and in the side constraint
6) The slide may have been slower than assumed
7) A two-stage failure mechanism is very plausible
Hendron, A.J. and Patton, F.D. (1985) - The Vaiont Slide, a Geotechnical Analysis Based on New Geologic Observations
of the Failure Surface. Technical Report GL- 85-5, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.
Hoek, E. (1997) - General 2-dimensional slope stability analysis. Analytical and Computational Methods in Engineering
Rock Mechanics, 95-128, E.T. Brown, Ed., Allen and Unwin, London.
Hungr, O., Salgado, F.M. and Byrne, P.M. (1989) - Evaluation of a three-dimensional method of slope stability analysis.
Canadian Geotechnical Journal, 27: 679-686.
Romero, S.U. and Molina, R. (1974) - Kinematic aspects of the Vaiont Slide. Proceedings, 3rd. Congress
ISRM, Denver, Colorado, 2:865-870.
Selli, R., Trevisan, L., Carloni C.G., Mazzanti, R. and Ciabatti, M. (1964) - La Frana delVajont. Giornale di Geologia. serie
20, XXXII (I), 1–154.
Superchi, L. (2011) - The Vajont rockslide: new techniques and traditional methods to re-evaluate the catastrophic event.
Ph.D. Thesis, University of Padova, 188p.