Failure of Vajont Dam, Italy
Group 14
Niall Pitcher
Shane Canavan
Eoin O Malley
Anne Glennon
Location and Background
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Located 100kms North of Venice in the Alps.
Constructed by a company called SADE to
provide hydroelectric power to the cities of
Milan, Turin and Modena.
1956-1960
265 metres high
Area Map
Design
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Designed as a doubly curved arched dam made
from reinforced concrete (360,000m³)
The dam was 3.4m thick at its crest widening out to
27m at its base, with the chord of the dam 160m
Volume of impounded water was 115 million m³
within the reservoir created from the dam
largest thin-arched dam in the world when it was
completed in 1960
Failure
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Studies into the soil surrounding the dam
concluded
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3 test borings had failed to identify areas of weakness;
It was assumed that any shear plane would have a
‘chairlike’ form and exert a ‘braking effect’;
Seismic analyses had suggested that the banks consisted
of very firm in-situ rock with a high Young’s modulus.
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Concluded that smaller slides in the looser
surface layers were likely (with low velocities and
volumes), deep-seated landslides were extremely
unlikely.
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November 1960-designers 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
Dam was drained down and filled up 3 times
to comtrol the creep rate, without failure
4th October 1960……….
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On 4th October 1960, 260 million m³ of earth
and rock slid 500m north at 110 km/hour
Landslide pushed a wave up the opposite
bank 260m above the original reservoir level
and then over-topped the dam by up to
245m.
30 million m³ of water fell on five villages
destroying them. 2500 people were killed
Reasons for Failure
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An increase in pore water pressure due to the
increasing level of the reservoir reducing the
effective normal strength and the shear resistance.
When the level was dropped hydraulic pressures
were induced as water in the jointed limestone tried
to drain. The force from this caused a brittle failure
and a loss of strength.
It is believed SADE were under pressure to sell the
dam and its generators to the newly formed stateowned electric company.