Accession Number:

ADA242569

Title:

Seismic Stability Evaluation of Ririe Dam and Reservoir Project. Report 2. Stability Calculations, Analysis, and Evaluations. Volume 1. Main Text

Descriptive Note:

Technical rept.,

Corporate Author:

ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS GEOTECHNICAL LAB

Report Date:

1991-09-01

Pagination or Media Count:

207.0

Abstract:

The man-made water retaining structure at the Ririe Dam and Reservoir Project, located on Willow Creek about 20 miles upstream of the City of Idaho Falls, Idaho, has been evaluated for seismic safety in the event of a Magnitude 7.5 earthquake occurring at the Grand Valley Graben, about 5 miles from the site. The construction history and the results of recent field and laboratory studies are documented in Report 1 of this series. This report documents the numerical analyses and engineering evaluation used to assess seismic stability. In general, it was concluded that Ririe Dam will be marginally safe if subjected to the design earthquake. Significant damage is expected to occur, however. Nearly all of the upstream random fill and upper portions of the gravel alluvium will liquefy as a consequence of the design earthquake. Slope stability calculations indicate, however, that the dam will remain stable because the magnitude of residual strengths for liquified materials is significant. Best estimates of permanent displacements are quite large up to 6 ft for the upstream side of the dam. The estimated displaced shape indicates that the crest will move vertically about 6 ft leaving a freeboard of 10 ft for the design pool.

Subject Categories:

  • Geology, Geochemistry and Mineralogy
  • Soil Mechanics
  • Seismology
  • Civil Engineering

Distribution Statement:

APPROVED FOR PUBLIC RELEASE