Loading Rate Effects on Compressibility of Sand

Stress-strain curves from 61 uniaxial strain tests are presented which depict the response of three dry sands to intense transient pressures; the loadings ranged from 10 MPa to 80 MPa and were applied with rise times ranging from a few tenths of a millisecond to a few minutes. Equipment and techniques used to conduct the tests and to assess the effect of wave propagation on the measurements are described. The data show that the resistance of dry sands to compression increases dramatically when loading rise times are less than 1 msec, and that the character of the stress-strain relation shifts rapidly from a stiffening response (curvature concave to stress axis) to a softening response (curvature concave to strain axis). The stress-strain response of a relatively simple rate-dependent rheologic model is shown to be in good agreement, both qualitatively and quantitatively, with the measured results.