دانلود رایگان مقاله پدیده بنیادی ماخ برای موانع دفن شده در خاک

Abstract

The paper investigates the explosion characteristics of a below ground event of an explosive charge in proximity to a rigid cylindrical obstacle. The two-dimensional study simulates a line explosive and a parallel long cylindrical structure. The investigation shows that the unloading branch has a negligible effect on the peak pressure envelope whereas shear behavior and explosives burning have a considerable effect and should not be disregarded. The effect of the soil’s equation of state and especially the full locking parameter on the pressure distribution on an obstacle has been studied. At a short standoff distance where a steep pressure growth beyond the full compaction point is developed, the pressure distributions envelope shows three maxima values that are located at some distance away from the axis of symmetry. It is different than the common single peak along the axis, in the case of a distant explosion. This effect is more pronounced for a medium having sharper pressure growth in the EOS beyond the full compaction point and for smaller charge standoff distances. The pressure distributions analysis indicates that the appearance of second (absolute-primary) and third (secondary) peaks are caused by the Mach stem effect appearing in a soil medium with full locking. The secondary peak pressure envelope maximum corresponds to the secondary Mach stem phenomenon that does not appear in the case of a planar wall, where the incident angle depends on the wave front curvature only.

6. Conclusions

An investigation of the explosion characteristics of a charge-line explosive in soil in proximity to a rigid cylindrical obstacleburied in soil has been carried out. The soil is modeled as an irreversible compressible medium with full bulk locking and dependence of the current deviatoric yield stress on the pressure. The parameters study for a nearby explosion shows that the loading branch of the equation of state has a dominant effect on the evaluation of the peak pressure envelope. Consideration of the soil shear behavior and explosives equation of state including the burning pocess have a major effect and should be taken into considaration to obtain a reliable quantitative prediction of the envelope shape. The pressure distribution along an obstacle has been studied for various values of the medium’s full locking parameter. For a short standoff distance and a steep growth of pressure beyond the full compaction point, the envelope of the pressure distributions shows three maximum values that are located at some distance away from the axis of symmetry opposed to a single peak at the axis of symmetry, as is the case for a distant explosion. This effect is more pronounced for the medium having sharper pressure growth in the EOS beyond the full compaction point and for smaller charge standoff distance. The pressure distributions analysis reveals that the second (absolute-primary) and third (secondary) peaks are caused by the Mach stem effect appearing in a soil medium with full locking. The Mach stem is first developed at the point, that corresponds to the primary maximum and later it is developed at the point, corresponding to the secondary maximum. Therefore, it may be concluded that this secondary maximum of the peak pressure envelope corresponds to the secondary Mach stem phenomenon that does not appear in the case of a planar wall, where the incident angle depends on the wave front curvature only. The development of the first peak requires further studies that are beyond the scope of this paper.