Please use this identifier to cite or link to this item: https://hdl.handle.net/11681/11028
Title: Finite-element calculations of Foam HEST 1
Authors: United States. Defense Nuclear Agency
Windham, Jon E. (Jon Enrique)
Keywords: Backfills
Shallow-buried structures
Underground structures
Finite element method
Simulation
Foam HEST 1
Soil-structure interaction
Soil mechanics
HE explosions
Blast effects
Explosion effects
Underground tests
Publisher: Structures Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; SL-80-1.
Description: Miscellaneous Paper
Abstract: The results of analytical studies are presented in which the HONDO dynamic finite-element (FE) code was used to perform (1.) a two-dimensional (2D), planestrain calculation of the Foam HEST 1 test event, (2.) a second 2D calculation identical with the first except that the backfill properties were changed from those of the sand used in Foam HEST 1 to those of a hypothetical low-strength clay, and (3.) companion 1D calculations for a section through the backfill, a section through the center of the roof, and a section through the sidewall of the structure. For locations in the backfill above and/or well away from the structure, vertical stress-time histories from the 2D calculation were in good agreement with those measured by the vertically-oriented stress gages in Foam HEST 1. The calculation also did a good job of replicating the intense 1-ms-duration initial loading pulse on the center of the roof as well as the early- time roof loading near the sidewalls. Early-time particle velocity comparisons in the sand backfill were reasonably good, but the measurements after about 5 ms appear to have been significantly influenced by relatively compressible native soil materials beneath the backfill which were not modeled as such in the calculation. The calculated displacement of the center of the roof agrees very well with the measured response up to 8 ms; however, the calculated peak displacement was 3.4 cm at 12 ms, while the measured peak was approximately 20 cm at 35 ms. The peak stress and impulse delivered to the center of the roof were higher for the clay backfill calculation than for the sand backfill calculation. Stress and impulse over the sidewall, however, were greater for the sand backfill case. The maximum relative deflection of the center of the roof for the clay backfill was 3.2 cm and occurred at 8.5 ms, while that for the sand was only 0.6 cm and occurred at 3.2 ms. For shallow depths in the backfill, the agreement between 1D and 2D calculations of vertical stress was excellent for both sand and clay; for deeper locations in the clay, the 2D calculation histories were significantly altered by waves coming through the native soil ahead of those traveling directly through the backfill. For a 1D section through the center of the roof, stresses computed in both the sand and the clay backfills were in excellent agreement with the 2D results for at least 3 ms. For locations near the structure corners, however, results from 1D calculations can be misleading.
Rights: Approved for public release; distribution is unlimited.
URI: http://hdl.handle.net/11681/11028
Appears in Collections:Miscellaneous Paper

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