1. 4-4. landslide 4-4-1. Introduction
Definition: Movement of mass on a slope (due to gravity)
Movement can be fast or slow
Slide, slip, fall, or creep
The mass can be soil, debries, rocks, and water mixtures
July 27, 2011 landslide on the slope of Umyeon Mt., Seoul:

2. 27 March 2014 - 10:15am, Buynaksk-Gimry road blocked by landslide

4. Types of Landslides
Slides: Blocks of material moving on well-defined shear planes
Rotational slides: Moving along a concave surface
Translational slides: Moving parallel to the ground surface
Falls: Sudden release of rocks or soils dropping freely through the air with little contact with other surfaces until impact
Topples: Similar to falls except that the initial movement involves a forward rotation of the mass
Flows: Moving entirely by shearing within the transported mass and act like viscous fluids
Creep: Almost imperceptible movement of material down a slope
Lateral spreads: Occurring when liquefaction in underlying materials causes surface rocks or soils to move down gentle slopes

7. Slope Stability

8. Factors affecting slope stability
(Geological) structure, esp. joints, foliations, bedding and other layered structures
Mass on the slope
Types of the mass
Water
Climate (esp. T. and pptn.)
Plantation
Time

9. Joints, faults, bedding planes, or any planar feature that interrupts cohesion is a risk for slope instability. Water will preferentially travel down such features, weakening them by reducing resisting forces and by weathering the minerals therein. Chemical and physical weathering play roles in slope destabilization.

10. Water: small amounts increase cohesion, but add too much and it causes particles to lose contact with one another reducing both friction and cohesion.
Angle of repose: this is the maximum angle of a stable slope as determined by the friction, cohesion, and particle shape

11. Vegetation:
Roots penetrate regolith and tend to bind particles together as well as absorb water. They are a stabilizing force on slopes.
Here we see the result of vegetative loss due to fire and the resultant mass movement

12. 4-4-3. Development and Landslide
Generally, landslide more frequently occurs upon development
Causes of more frequent landslide
Making geologic conditions adverse
Water seepage
Artificial alteration (change) of the slope

13. Landslide caused by the rupture of a water supply pipe. Source: AIR
Caused by Abruzzo (Italy) Earthquake 4/23/2009 3:00:00 PM

14. Both natural and artificial processes can alter slope
Both natural and artificial processes can alter slope. As streams (or construction) cut into a bank, slope is increased, thereby increasing the downslope forces.
Eventually the driving force becomes too great and failure occurs

15. 4-4-4. Recognition & Protection
Recognition of possible landslide slope from
Geological survey
Landslide history (frequency)
Slope stability map
Various signs
Fractures on walls
Distortion of the door (window) frames
Out of alignment of the fence bars
Water leakage at the basement of the slope

16. Slope-stability index distribution for a calibration region on Oahu

17. Fracture on the bottom floor of a building at the event of landscape in 2007. Maine, USA.

19. Reducing the risk by
Drainage improvement
Decreasing slope angle
Construction of retaining walls
Rock bolting

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