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Landslide Hazards: Causes, Consequences, and Management

This course explores the causes, consequences, and management of landslide hazards. Topics include types of landslides, warning systems, slope management, and field excursions. Learn how to predict and prevent landslides.

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Landslide Hazards: Causes, Consequences, and Management

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  1. 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

  2. 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

  3. New Book Published October 2008

  4. 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

  5. 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.

  6. 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

  7. 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 • >>>>>>>>>>>>>>>>>>>>>

  8. 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

  9. Landslides: Removing the Consequence Manchester Main Manchester – Sheffield Road (A625) Alternative route – only suitable for light vehicles – gradient of 1 in 4 1 km

  10. 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

  11. Landslide in man made Cut Slope at km 365 west of Sao Paolo - August 2002 berms Heave at toe

  12. berms Steep scar to rotational failure

  13. 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

  14. 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 

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