1. The document discusses understanding the role of damage mechanisms and kinematics in large landslides. 2. Damage occurs both externally in the slope and internally through fracturing, and there are various types of damage related to factors like slope geometry and lithology. 3. Kinematics influence the failure mechanism and volume, and both damage and kinematics must be considered and modeled to understand landslide mechanics.

1. Simon Fraser University
Engineering Geology and Resource Geotechnics
Research Group
Understanding the Mechanics
of Large Landslides
Doug Stead, Simon Fraser University
and
Erik Eberhardt, University of British Columbia

2. Outline
1. What is the role of damage mechanisms in
large landslides?
2. What is the role of kinematics in large
landslides?
3. How can we model damage and kinematics
effectively in large landslides?
SFU

3. St Jouin Bruneval July 2013
VIDEO-FRACTOGRAPHY – a window on damage and kinematics

4. Damage and Kinematics
1
2
3
4

5. Rock Slope Damage
Spatial Damage
•
•
•
•
•
•
Slope topography
Failure surface morphology
Failure surface geometry
Failure mechanism
Lithological variations
Geological structure
Dx – along slope
Dy – in slope
Dz – depth
DT – Time
Temporal Damage
• Geologic processes
• Tectonics – deformation
phases, uplift-erosion
• Geomorphic processes –
• Earthquakes
• Groundwater/Thermal
• Long term creep
•
•
•
•
Preconditioning
Initiation
Failure
Post-failure
SFU

6. External and Internal Slope Damage
Tension
cracks
Sackungen
Frank Slide
Palliser, AB
Newhalem
SFU

7. VAJONT : Geomorphic External Damage
VAJONT : Geomorphic External Damage
APPROACH
• Geomorphic damage mapping to constrain
mechanisms and models
• Consider landform evolution and influence
on slope failure mechanism –
“Geomorphic Stress Path”
Wolter et al. 2013
SFU

8. Damage - Failure Surface Geometry & Mechanisms
PLANAR
ACTIVE-PASSIVE SLAB
UNDULATIING
FLEXURAL TOPPLING
MULTIPLANAR
DAMAGE SHAPE FACTOR
SFU

9. Structural Controls on Rock Slope Damage
SFU

10. Lithological Controls on Rock Slope
Damage
SFU

11. Temporal Damage: Monitoring
SFU

12. Simulated Inverse Velocity and Crack
(Damage) Development in SLOPE MODEL
Damage Zone
SFU
12

13. Kinematics and Block Shape:
Pentahedral wedges
SWedge
RocScience 2013
SFU
13

14. Rotation vs. Translation
3DEC
Rock Cut
Vajont
Aknes
Siromodel
SFU

15. Release Surface: Questions
TYPE
INFLUENCE ON MECHANISM – DAMAGE/MOVEMENT DIRECTION
INFLUENCE ON VOLUME (Runout)
IS 2D OR 3D ANALYSIS
REQUIRED ?
PERSISTENCE-SPACING CONSIDERATIONS – Rock bridges?
GEOMORPHIC RELEASE – LANDFORM EVOLUTION
INFLUENCE OF EXCAVATION
GROUNDWATER/IN-SITU STRESS
SFU

16. Release Surfaces and Kinematics
SFU

17. Modelling Damage and Kinematics
TOOLBOX
SELECTION OF
MODEL TYPE
LIMIT
2D or 3D ?
CONTINUUM
HYBRID
DISCONTINUUM
EQUILIBRIUM
“Adapt the model to the problem NOT the problem
to the model”
“Large Landslides are an Energy-Damage System”
SFU

18. Brittle Fracture Modelling: ELFEN
SFU

19. Brittle Fracture Modelling: UDEC
VAJONT
Gao 2013
SFU

20. UDEC and
3DEC
Brittle
Fracture
SFU
20

21. Importance of Kinematics – Vajont
Prandtl Zone
Models stable unless:
• block size decreases
kinematic release
• internal deformation is allowed
internal strain accommodation
2D – Phase2
Wolter et al. 2013
Prandtl Zone
3D – 3DEC
3D – Slope Model
SFU

22. Slope Model Damage Simulation - Vajont
• Point cloud (airborne LiDAR) derived geometry
• Discontinuity sets are derived from photogrammetry and field
mapping
• Groundwater is considered implicitly (i.e. decreased friction
angle) and explicitly
Wolter et al. 2013
SLOPE MODEL: Point-masses
connected by Springs
SFU
22
Cundall, 2011

23. VAJONT PHOTOGRAMMETRY

24. f=800mm PHOTOGRAMMETRY

25. Preliminary Vajont Slope Model- Dry
Model
fracturing
Before
failure
Wolter et al. 2013
Model
displacement
After
failure
SFU
25

26. Preliminary Groundwater Model
G.W.
300 m
Sliding surface
Havaej et al. 2013
SFU
26

27. Conclusions
1. Damage is a fundamental component of the mechanics of
large landslides
2. Extensive records exist of external damage
3. More limited data on internal damage but recognized as
extremely important (a “damage front” concept)
4. It is important to consider the inter-relationships between
failure kinematics and brittle rock fracture in rock slopes
5. Preliminary work show possible relationships between
deformation and rock bridge fracture.
6. Improved characterization of large landslides should
combine and fully utilize the latest developments in
remote sensing-monitoring and modelling technologies.
SFU