Mine Blast Loading: Experiments and Simulations
Technical rept. Jul 2007-Apr 2009
SOUTHWEST RESEARCH INST SAN ANTONIO TX
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A series of mine-blast loading experiments were conducted where the soil moisture content, plate standoff distance, and plate shape flat and V-shaped were varied. Three experiments were conducted for each test configuration to quantify repeatability of the experiments. The primary experimental diagnostic was the initial velocity imparted to the plate, as inferred from the maximum height that the plate displaced. Numerical simulations were conducted to examine the ability to reproduce the experimental measurements using the wavecode CTH and a modified soil equation of state EOS developed by Kerley. The EOS explicitly accounts for soil moisture content and initial distension porosity. It was found that the initial soil density was extremely important in reproducing the experimental results. It is shown that the simulations reproduce, within experimental variability, the momentum transferred from the mine blast loading by the soil and detonation products for the flat plate experiments as a function of moisture content and plate distance. However, it was found that the simulations overpredicted the momentum transferred to the V-shaped plates by approximately 50. We investigated the root cause for this discrepancy. The simulations calculate a turbulent-like flow field characterized by small-scale vorticity eddy structures that can only be resolved at the resolution of the grid. The absence of viscous dissipative terms Reynolds stresses in the momentum and energy equations results in a coarsely resolved flow field that transfers too much energy to the plate. At finer grid resolutions, the mine blast products are less coherent due to the increased vorticity being generated and result in more localized loading on the plate by eddy flow structures. Although this provides better agreement with experimental results, we were not able to refine the computational grid sufficiently to reproduce the experiments.
- Soil Mechanics
- Land Mine Warfare