Enid Dam is a U.S. Army Corps of Engineers Dam constructed in the early 1950's. It is located in northern Mississippi approximately 12 miles south of the town of Batesville, Mississippi. It is one of four flood control dams in the Yazoo River Basin Headwater Project. Enid Dam is a rolled earth fill zoned embankment and is approximately 8,400 feet long and 85 feet in height above the valley floor. Its main function is flood control but it also provides for recreational activities. Due to its location near the New Madrid Seismic Zone, the source of three of the largest earthquakes in recorded U.S. history, a seismic safety investigation is being performed to determine the expected response of the dam to a major earthquake. The studies included: development of the design earthquake ground motions; field investigations including standard penetration testing, cone penetration testing, field vane shear testing, undisturbed sampling, and geophysical testing; analysis of liquefaction potential using recently published recommendations; evaluation of the post earthquake residual strength of the liquefiable soils using correlations of Cone Penetration Test (CPT) resistance to Field Vane Shear Test (VST) remolded strength; and analysis of post-earthquake seismic stability and expected deformations using static equilibrium slope stability analyses, and two-dimensional nonlinear finite element analyses with the computer codes FLAC and TARA3. The problem soil layers are alluvial fine-grained soils in the dam foundation that are expected to lose significant strength during a major earthquake. These materials are present throughout the Mississippi River Valley.
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