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|Title:||In situ seismic investigation, Fort Peck Dam, Montana|
|Authors:||United States. Army. Corps of Engineers. Omaha District.|
Curro, Joseph R.
Horn, John E.
Ballard, Robert F.
|Keywords:||Fort Peck Dam|
|Publisher:||Soils and Pavements Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: A geophysical site investigation consisting of surface refraction seismic, crosshole, downhole, R-wave dispersion, and vibratory tests was conducted along a typical cross section (sta 42+00) of Fort Peck Dam. Three levels along the cross section were selected for test locations: sta 0+35, 4+75, and 23+00. P- and S-wave velocities were determined as a function of depth from ground surface to bedrock. A reasonable amount of redundancy was incorporated into the test program to build a high level of confidence in the data obtained. P-wave velocities, which were obtained from surface refraction, crosshole, and downhole tests, could be collapsed into eight distinct zones along the sta 42+00 cross section. Velocities ranged from 1250 to 7200 fps. The saturated sand underlying the core from el 2060 to 2000 (elevations are in feet referred to mean sea level) was defined as a low-velocity zone with a P-wave velocity of 4600 fps. S-wave velocities for the most part showed a gradual increase with depth, ranging from 600 fps -for the near-surface materials to 1900 fps within the shale. No low-velocity S-wave zones were encountered.
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