Wave Propagation Studies In Laterally Confined Columns Of Sand

Wave-propagation Studies in Laterally Confined Columns of Sand

An experimental study of the relationship between pertinent wave-propagation parameters and the one-dimensional stress-strain behavior of two sands was conducted. The stress-strain relation for the sands was characterized by a nonlinear strain-hardening behavior. The nature of the stress-strain curve implied that shocks should form or be sustained in the soil. This phenomenon was studied by observing the dynamic and kinematic characteristics generated by a soft-fronted stress pulse applied at one end of a long slender column of laterally confined sand. To develop a method of predicting the kinematics of wave propagation from the stress-strain curve, the observed wave-propagation parameters were related to laboratory stress-strain curves. A unique sample container, loading system, and instrumentation system was developed. The experiments approximated one-dimensional conditions up to reflected stresses of 1,600 psi. The results indicated the shocking-up of the soft-fronted input pulse that could be predicted from the laboratory stress-strain curve. The particle-velocity versus wave-velocity relationships dictated the change in shape of the kinematic pulse and could be predicted using a secant modulus analysis technique. A very high stress versus time gradient (rise times less than 50 microsec) was observed to form as the wave propagated through the soil.

Technical Abstract Bulletin

Similitude Study of Flexible Buried Arches Subjected to Blast Loads

The objective of the study was to investigate and verify model-to-prototype scaling relations for blast loaded buried arches that respond both elastically and inelastically. Four geometrically similar, semicircular aluminum alloy arches with 4-, 8-, 12-, and 36-inch diameters were buried in dense dry sand and subjected to air-blast-induced loads on the surface. The tests were conducted at the Large Blast Load Generator located at the U.S. Army Engineer Waterways Experiment Station. The results of two series of tests, each consisting of 3 repeated shots, ranging from 70 to 300 psi, are presented. Within the range of parameters investigated, the scaling of the dependent variables were adequately verified. These variables included acceleration, velocity, displacement, thrust, and bending moment. (Author).