Piston Core Properties and Disturbance Effects

Abstract

Laboratory geotechnical data on piston cores from 31 sites on the mid‐Atlantic Upper Continental Slope show the near‐surface sediments vary from normally consolidated to somewhat overconsolidated clayey silts and silty clays of low to high plasticity. They also exhibit normalized behavior and their index property correlations with the effective‐stress friction angle, the undrained strength ratio, and the compression index are reasonably consistent with existing knowledge. Disturbance effects were effectively minimized in the consolidation and strength parameter determinations by using stresses and stress histories in excess of those in situ. However, substantial disturbance effects in preconsolidation stress determinations were found. The preconsolidation stress values derived from the triaxial data are high, and those from the consolidation data are low, compared with the values obtained from the laboratory vane data. Because existing knowledge concerning disturbance effects suggests that in‐situ preconsolidation stress values should lie between those derived from the triaxial and laboratory vane data, the preconsolidation stress values obtained from the consolidation data appear to be appreciably smaller than in‐situ values.