WAVE-PROPAGATION STUDIES IN LATERALLY CONFINED COLUMNS OF SAND.
Technical rept. Jan 65-May 66,
NEW MEXICO UNIV ALBUQUERQUE ERIC H WANG CIVIL ENGINEERING RESEARCH FACILITY
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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.
- Soil Mechanics