1. Group 14 Angelina Hand Mark Kelly Lydia Rooney Seán Stapleton

2. Vajont Dam, Italy 100km north of Venice Constructed between 1956 and 1961 Built to provide power to Milan, Modena and Turin Largest double-arched dam in the world when it was completed One of UNESCO’s five worst man-made disasters caused by engineers and geologists!

3. Design 262m tall 27m thick at base and 3.4 m thick at top 150 million m 3 of water retained behind the dam 360,000m 3 of reinforced concrete

4. 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!

5. 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 control the creep rate to avoid failure

6. Failure October 9 th 1963: Landslide occurred Mass of 260 million m 3 slid into river at 110km/hour Caused 50 million m 3 of water from the reservoir to be swept over dam in a 250 m high wave Over 2000 lives lost 5 villages destroyed Dam remained fairly intact Only top 1m washed away

7. 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

8. 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

9. Animation http://www.youtube.com/watch?v=uqkFXm2HtMA&f eature=related