1 ENV-3A1Y: Natural Hazards: Landslide Hazards N.K. Tovey Н.К.Тови Landslide on Main Highway at km 365 west of Sao Paulo: August ,607 days ago today Exactly 40 years ago next Saturday

2 Lecture 1: Wednesday Week 42 –Introduction Landslides as a Hazard and their consequences background to why they occur Lecture 2: Thursday Week 4 12 – 13 EF 1.01 –Types of Landslide Lecture 3: Thursday Week –Landslide Warning systems Lecture 4: Wednesday Week 5 09 – 10 EF 1.01 –Landslide and Slope Management Field Excursion: Thursday Week 5 12 – 17 Bring Field Clothing and a packed lunch ENV-3A1Y: Natural Hazards:

3 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:

4 Landslides as a Hazard Grossly Under Represented as a Hazard Often treated as a secondary issue e.g Rain Storm Disasters of 18 th June 1972 in Hong Kong 2 major landslides each killing over 60 people No one was killed by drowning/flooding ENV-3A1Y: Natural Hazards: Failure of slope above Po Shan Road in June 1972

5 Landslides associated with Heavy Rain (Tropical Cyclones) –~ 500+ landslides affected man in Hong Kong 28 th May to 2 nd June –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:

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

7 Aberfan: 21 st October 1966 Tip 7 collapsed, engulfed Pantglas School and parts of the village killing 144 mostly children ENV-3A1Y: Natural Hazards:

8 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 (F s ): Forces resisting landslide movement arising from the inherent strength of the soil. Forces trying to cause failure (i.e. the mobilizing forces). F s = ENV-3A1Y: Natural Hazards: F s > 1 stable But is it? F s = 1 just stable F s < 1 unstable But is it?

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

10 berms Steep scar to rotational failure

11 Landslide Geochemistry