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ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10. Landslide Hazards N.K. Tovey Н.К.Тови. 15,699 days ago today 43 years ago next Wednesday. Lecture 4. Lecture 3. Lecture 1. Lecture 2. Landslide on Main Highway at km 365 west of Sao Paulo: August 2002.

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env 3a1y envf3a1y natural hazards 2009 10

ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10

Landslide Hazards

N.K. Tovey

Н.К.Тови

15,699 days ago today

43 years ago next Wednesday

Lecture 4

Lecture 3

Lecture 1

Lecture 2

Landslide on Main Highway at km 365 west of Sao Paulo: August 2002

env 3a1y envf3a1y natural hazards 2009 101
ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10
  • Lecture 1: Wednesday Week 4 09 – 10 Lab A
    • Introduction
      • Landslides as a Hazard and their consequences
      • background to why they occur
  • Lecture 2: Thursday Week 4 12 – 12:50 CD Annexe 0.01
      • Types of Landslide
  • Lecture 3: Wednesday Week 5 09 – 10 CD Annexe 0.01

[ but may be in Lab A depending on how things goes in Week 1]

      • Landslide Warning systems
  • Lecture 4: Thursday Week 5 12 – 12:50 CD Annexe 0.01
    • Landslide and Slope Management
    • Field Excursion: Week 4 or Week 5 starting at 12:55
    • from bus stop [watch email for details]
      • Bring Field Clothing and a packed lunch – meet at CD annexe Bus Stop
env 3a1y envf3a1y natural hazards 2009 102
ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10
  • Aims of the course
  • An introduction to Landslide Hazard Management
  • Factor of Safety
  • the causes
  • Why they occur
  • Can we predict them
  • the consequences
  • The types of landslide
  • Landslide Warning –
  • Development of the Hong Kong System and what was learnt
  • Strategic Planning for the future
  • Slope management
env 3a1y envf3a1y natural hazards 2009 103
ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10

Failure of slope above Po Shan Road in June 1972

Landslides as a Hazard

  • Grossly Under Represented as a Hazard
  • Often treated as a secondary issue
      • e.g Rain Storm Disasters of 18th June 1972 in Hong Kong
      • 2 major landslides each killing over 60 people
      • No one was killed by drowning/flooding or as a result of the typhonn.
env 3a1y envf3a1y natural hazards 2009 104
ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10

Landslides associated with

  • Heavy Rain (Tropical Cyclones)
    • ~ 500+ landslides affected man in Hong Kong 28th May to 2nd June 1982.
    • As a result of NKT’s actions Yuen Mo village ceased to exist.
  • Earthquakes
    • Cause liquefaction and rise of pore pressures
  • Volcanic Eruptions
slide7

ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10

  • 15699 days ago today at 09:15
  • N K Tovey a second year PhD student was listening to a lecture by Andrew Schofield.
  • Theme of lecture was Landslide Hazards
  • At 09:15 he turned his attention to a landslide disaster which had occurred a few year earlier in Belgium.
  • A colliery tip collapsed killing around 20 people in the village.
  • At precisely the time he was speaking about the disaster
  • >>>>>>>>>>>>>>>>>>>>>
slide8

ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10

  • Aberfan: 21st October 1966
  • Tip 7 collapsed, engulfed Pantglas School and parts of the village killing 144 mostly children
slide9

Landslides: Removing the Consequence

Manchester

Main Manchester – Sheffield Road (A625)

Alternative route – only suitable for light vehicles – gradient of 1 in 4

1 km

env 3a1y envf3a1y natural hazards 2009 105
ENV-3A1Y/ENVF3A1Y: Natural Hazards: 2009 - 10
  • Geotechnics – the discipline needed for detailed analysis
      • "the application of the laws of mechanics and hydraulics to the mechanical problems relating to soils and rocks"
  • Factor of Safety (Fs):

Forces resisting landslide movement arising from the inherent strength of the soil.

Fs =

Forces trying to cause failure

(i.e. the mobilizing forces).

Fs> 1 stable

But is it?

Fs = 1 just stable

But is it?

Fs < 1 unstable

slide12

berms

Steep scar to rotational failure

slide13

GIS

Remove Consequence

Remedial Measures

Safe at the moment

Man’s Influence (Agriculture /Development)

Cut / Fill Slopes

Pumping

Drainage

Construction

Hydrology (rainfall)

Earthquakes

Geology

Ground Water

Ground Loading

(Consolidation)

Erosion/Deposition

Glaciation

Weathering

Surface Water

Material Properties (Shear Strength)

Geochemistry

Stability Assessment

Slope Profile

Landslide

Preventive Measures

Slope Management

Design

Landslide Warning

Landslide

Cost

Build

Temporarily Safe

No Danger

Consequence

relationship between mobilizing resisting forces
Relationship between mobilizing & resisting forces

S1

S2

S3

N1

N2

N3

S

W

S

S

W

W

N

N

N

=W

Shear Force

Normal Force

Force (S) required to move block is proportional to Normal Force (N)

On a slope

N depends on weight and 

N = W cos 

S also depends on weight and 

N = W sin 