Malpasset Problem

Cracking was noticed near the base on the downstream side of the dam, but it was not investigated. It is undetermined when these cracks appeared. Just weeks after the cracks were noticed, on December 2, 1959, a terrible disaster occurred: the dam failed, killing possibly 500 people. Little remained of the dam; failure had been sudden and catastrophic. The dam swung open and released the reservoir water. The dam itself soon broke away from the abutments and travelled downstream.
Looking upstream, part of the wing wall remains on the left abutment.	Almost nothing remains on the right abutment.
photos courtesy of Russ Collins, Provence-Beyond
Investigation and numerous studies commenced following the dramatic failure. No other dam of its type had failed before or since. A tectonic fault was identified on the downstream side of the dam that was not realized during design or construction because of its distance from the dam. Analyses of the dam were performed to try to determine the cause of failure, concentrating on the following: concrete stresses buckling of the arch sliding of the abutment block sliding of the dam at the contact with rock sliding on the downstream fault. But none of these resulted in a definitive answer. A combination of unusual pressure build-up under the dam, the state of the rock on the left bank, and the downstream fault were proposed as the cause of the failure. Heavy rain just before the failure had increased the reservoir level by more than 15 feet; this also is thought to have contributed to the failure by increasing the pressure under the dam. No simulations of the dam or its foundation are available for review.