Groundshock Displacements–Experiment and Simulation

Abstract

A basic work on groundshock experimental measurement and numerical modeling and simulation is described. The work includes measurement of groundshocks caused by an above ground FAE explosion, soil data collection and interpretation and numerical simulation. An anti-minefield ‘Carpet’ system charge was initiated above ground in order to form a FAE cloud detonated on ground surface. Tri-axial seismograms were measured at different ranges.

Reproduction of these measurements in a numerical simulation requires the knowledge of soil properties such as density, elastic moduli, compressibility and strength envelope. In order to determine these properties, soil density measurements, a refraction survey, direct shear tests and pressiometer tests at various ground depths were performed. The soil properties were used in MSC.Dytran numerical simulation. The DYMAT14 soil and crushable foam material model was used to model the soil. At ranges equal to and greater than 30 m the maximum radial and vertical displacements show a very good agreement (less than 0.05 mm difference) between experimental and numerical results. At shorter ranges the experimental results are jumpy and much higher than the numerical results. It is assumed that in the experiment, the close range sensors, being attached to the ground surface by 10 cm long pegs, were released by the explosion effect.

The results of this work show a numerical prediction capability of long range groundshock effects. No soil properties calibration was needed in order to fit numerical and experimental results. Further work is needed to get reliable measurements and numerical validation of groundshocks at close ranges, especially groundshocks caused by buried HE detonations coupled with large crater formation.