Effect of Soil Locking on the Cylindrical Shock Wave’s Peak Pressure Attenuation

Abstract

The paper investigates the characteristics of propagating shock waves in soil, resulting from an explosion of a cylindrical line charge. The main purpose of this investigation is to study the full locking parameter's effect on the qualitative and quantitative behavior of the peak pressure attenuation. The soil is modeled as a bulk irreversible compressible elastic plastic medium, including full bulk locking and dependence of the current deviatoric yield stress on the pressure. The Lagrange approach and the modified variational-difference methods are used to simulate the process. A study of the characteristics of the equation of the state of soil was carried out for the case of a cylindrical line charge explosion in an infinite soil medium. The computed results were compared with experimental data. It was found that the full locking model somewhat overpredicts the measured stresses. The dependence of the peak stress attenuation, during the shock wave propagation, on the full locking parameter of the equation of state was studied. When the pressure-volumetric strain relationship beyond the point of full compaction is not steep, the attenuation may be described by a power law that may be expressed as a linear relationship on a logarithmic scale. When this relationship is relatively steep however, the logarithmic dependence of the peak stress on the shock wave coordinate is close to a bilinear function. It was also shown that the shock wave peak stress parameters of this power law for the high pressure range (i.e., short distance of the wave front from the explosive charge) are linearly dependent on the full locking parameter. Also it was shown that the full compaction density affects the exponent of stress-distance power relationship only at the earlier stage of the wave propagation and only when the range of nonlinear elastic compaction is relatively narrow.