The Vaiont Slide. A Geotechnical Analysis Based on New Geologic Observations of the Failure Surface. Volume 1. Main Text
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB
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The study confirmed that the Vaiont Slide was a reactivation of an old slide. The slide moved upon one or more clay layers which were continuous over large areas of the surface of sliding. Three-dimensional stability analyses were required due to the magnitude of the upstream inclination of the clay layers forming the base of the slide. The angle of shearing resistance of the clay layers was determined to be about 12 degrees. The fluid pressure distributions used were consistent with the only piezometric data available before the 1963 slide and with an interpretation of the local groundwater flow system including the presence of karstic terrain above the slide. Results of the analyses completed for key periods in the history of the slide agree with the known slide behavior during these periods. The results also indicate that the reduction in the factor of safety caused by reservoir filling alone was approximately 12 percent, while the reduction caused by rainfall or snowmelt ranged from 10 to 18 percent. Correlations made between cumulative precipitation, reservoir levels, and slide movement records provide a well- defined failure envelope. These results explain why the slide was unstable at a given reservoir level and later stable at the same level. Conclusions from these correlations are consistent with the results of the stability analyses. The results of the study also suggest that the slide could have been stabilized by drainage.
- Geology, Geochemistry and Mineralogy
- Civil Engineering