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Title: Constitutive Properties for Undisturbed Marine Sediments in Support of the Subseabed Disposal Program
Authors: Akers, Stephen A.
Keywords: Marine sediments
Mathematical models
Publisher: U.S. Army Engineer Waterways Experiment Station
Abstract: A laboratory material property investigation was conducted on newly acquired undisturbed samples of Pacific illite in order to quantify the effective-stress, stress-strain and strength properties of the material when subjected to high-pressure, static and dynamic loading, conditions. The laboratory testing program consisted of triaxial shear (TX), hydrostatic compression, and uniaxial strain (UX) tests. Consolidated-undrained static TX tests with pore pressure measurements resulted in an effective-stress Mohr-Coulomb friction angle and cohesion intercept-of 28.6 degrees and 0.004 MPa, respectively. Comparable static and dynamic tests indicated that the undrained shear strength of undisturbed Pacific illite increased nominally 200 percent for an increase in strain rate from 10-6/second to 1/second. In terms of total stresses (up to 35 MPa), Pacific illite was observed to behave as a = 0 material in shear. Constrained modulus values derived from consolidated-undrained test results exhibited an expected dependence on specimen density (and/or effective consolidation stress). UX tests conducted to investigate loading rise time effects, however, produced divergent results. Two dynamic tests (with 36-millisecond rise times) performed on virgin specimens exhibited negligible increases in undrained constrained modulus compared to static test results (with 300-second rise times). In contrast, two multiply-loaded test specimens (with sequential rise times of 300 seconds, 100 milliseconds, and 36 milliseconds) showed a modulus increase of 20 percent by the third load cycle. Drained UX tests were successfully accomplished to stress levels in excess of 50 MPa and strains in excess of 60 percent. Representative static and dynamic laboratory test results were selected for future use by constitutive modellers in characterizing the response of undisturbed Pacific illite. At the request of the sponsoring agency, several drained hydrostatic creep tests were also conducted as part of this investigation.
Description: Report
Rights: Approved for Public Release; Distribution is Unlimited
Size: 4.34 MB / 138 pages
Types of Materials: PDF/A
Appears in Collections:Non-Series Report