Yielding and Locking of Confined Sand

Abstract

Experimental results of the stress-strain behavior of sand during confined compression, starting from some initial stress, show that the stress-strain curve is S-shaped, with yielding for small stress changes and locking as the stress change is increased further. In addition, the modulus during small stress changes is found to be consistent with the modulus backfigured from seismic wave velocity. Theory for the behavior of a regular array of elastic spheres is used to help explain these results. The effect of rate of loading is shown by experiment. On the basis of these findings, either plastic or shock waves can occur in sand, depending on the magnitude of the initial stress and the stress change. The modulus of compression during a dynamic loading can be significantly less than indicated by seismic velocity.