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ENV-3A1Y/ENVF3A1Y: Natural Hazards:

2008 - 9Landslide Hazards

N.K. Tovey

Н.К.Тови

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

14,971 days ago today

41 years ago next Sunday

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• Lecture 1: Wednesday Week 4 Lab A– Introduction

• Landslides as a Hazard and their consequences• background to why they occur

• Lecture 2: Thursday Week 4 12 – 12:50 Arts 01.01– Types of Landslide– For Group F only

• Field Excursion: Thursday Week 4 13 – 17• Bring Field Clothing and a packed lunch – meet at Union House

Turnround• Lecture 3: Wednesday Week 5 09 – 10 Lab A or Arts 01.01• [watch email for details]

– Landslide Warning systems• Lecture 4: Thursday Week 5 12 – 12:50 Arts 01.01

– Landslide and Slope Management– For Group R only

• Field Excursion: Thursday Week 5 13 – 17• Bring Field Clothing and a packed lunch – meet at Union House

Turnround

ENV-3A1Y: Natural Hazards: 2007 - 8

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• 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: Natural Hazards: 2007 - 8

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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

Failure of slope above Po Shan Road in June 1972

ENV-3A1Y: Natural Hazards: 2007 - 8

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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

ENV-3A1Y: Natural Hazards: 2007 - 8

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ENV-3A1Y: Natural Hazards: 2007 - 8

14607 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

>>>>>>>>>>>>>>>>>>>>>

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• Aberfan: 21st October 1966

• Tip 7 collapsed, engulfed Pantglas School and parts of the village killing 144 mostly children

ENV-3A1Y: Natural Hazards: 2007 - 8

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• 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.

Forces trying to cause failure(i.e. the mobilizing forces).

Fs =

ENV-3A1Y: Natural Hazards: 2007 - 8

Fs > 1 stable But is it?

Fs = 1 just stable Fs < 1 unstable

But is it?

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berms

Heave at toe

Landslide in man made Cut Slope at km 365 west of Sao Paolo - August 2002

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berms

Steep scar to rotational failure

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Landslide

Geochemistry