Mach stem due to an underground explosion near a rigid structure buried in soil

This paper presents recent results of an analysis of pressure distributions along the circumference of underground structures of various shapes due to a nearby buried explosion. The present study examines the effect of the standoff distance on the results and special attention is given to the soil medium equation of state characteristics and their effect on the Mach stem. It was found that for a short standoff distance and a steep growth of pressure beyond the full compaction point that characterizes dense soils, the envelope of the pressure distributions shows a maximum value, which is located at some distance away from the plane of symmetry rather than along it, as is the case for a distant explosion. This phenomenon causes the distortion of the frontal part of the explosive cavity. This effect is more pronounced for more dense soils that show a sharper pressure increase in the equation of state. It has been proven that these pressure distributions and associated shapes of the explosion cavities are caused by the Mach stem effect appearing in a soil medium with full locking.