Transcript Vajont_Dam[1].pptx

Group 14
Angelina Hand
Mark Kelly
Lydia Rooney
Seán Stapleton
Vajont Dam, Italy
 100km north of Venice
 Constructed between 1956 in 1961
 Built to provide power to Milan, Modena and Turin
 Largest thin arched dam in the world when it was
completed
 One of UNESCO’s five worst man-made disasters
caused by engineers and geologists!
Design
 262m tall
 27m thick at base and 3.4 m thick at top
 150 million m3 of water retained
behind the dam
 360,000m3 of
reinforced
concrete
Signs of Failure: Construction
Phase
 Concerns for stability of valley walls during
construction
 Tests showed possibility of ancient landslide on right
bank
 Concluded that smaller slides in looser surface layers
were likely
 BUT that deep seated landslides would be extremely
unlikely!
Signs of Failure: Filling of the
Reservoir
 March 1960: First small landslide occurs
 October 1960: Rate of displacement of 3.4cm/day
 November 1960: Large landslide
 Engineers realised that the large mass of the left bank was
unstable
 Used varying levels of water and drainage tunnels to gain
control of the sliding mass
 For the next two years dam was drained down and filled up
3 times to comtrol the creep rate, without failure
Failure
 October 9th 1963: Landslide occurred
 Mass of 260 m3 slid into river at 110km/hour
 Caused 50 million m3 of water from the reservoir
to be swept over dam in a 250 m high wave
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Over 2000 lives lost
5 villages destroyed
Dam remained fairly intact
Only top 1m washed away
Causes of Failure
 Increased water levels caused increased pore water
pressure in clays
 Reduced effective strength and shear resistance
 When dam levels dropped, hydraulic pressures were
induced
 Caused brittle failure and disastrous loss of strength
Conclusion
 Safe and sound structure
 BUT
 Emphasis on impacts of construction on surrounding
environment
 Importance of soil testing
 Town planning development of escape routes and
protection from floods