Shear Wave Generation of Near Surface Spall
Abstract
Very near field data were obtained from several in situ, dynamic material properties tests. The explosive driver of the tests was either a rectangular or circular explosive array placed on the surface and covered with an earthen berm. The tets were fired over several different types of alluvium. Following the initial compression and partial rebound, acceleration wave forms show -1 g dwells followed by an impulsive rejoin. This was identified as spall. The spall appears to be caused by shear waves initiating from the finite edges of the explosive source. The shear waves tend to force the material, both under and beyond the explosive array, upward until the soil fails and falls with a -1 g acceleration. The alluvium beneath the charge remains in compressive strain throughout the entire spall signature. Calculations verified this mechanism. The planar explosive array may be thought of as an approximation to a surface point source. This would suggest that shear waves are a viable mechanism for spall observed near surface burst experiments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1984
- Accession Number
- ADA140849
Entities
People
- Eric Rinehart
Organizations
- Air Force Research Laboratory