Strength behavior of marine sands and elevated confining stresses

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A testing program was initiated to determine the stress-strain and strength behavior of two very different marine sands (a calcareous sediment from South Australia and a siliceous sediment from the United Kingdom) at elevated confining pressures. The testing matrix consisted of a series of isotropically consolidated, undrained (CIU) and drained (CID), triaxial compression tests on samples of naturally deposited calcareous and siliceous sediment and remolded calcareous sediment. It was found that the calcareous samples displayed little cemented behavior during shear. For tests conducted at pressures up to 1.5 M Pa, a significant amount of particle crushing occurred in the calcareous samples but not in the siliceous samples. Particle degradation and reorientation facilitates transitions from dilative to contractive behavior with increases in confining stress. The calcareous sediment exhibited contractive behavior at confining pressures above approximately 500 kPa and the siliceous sediment remained dilative at stresses up to 1 M Pa during undrained loading. Comparison with data collected by the University of Sydney (CID tests with confining pressures up to 60 M Pa) showed that most of the variations in strength behavior occurred within the low stress range (up to 2 M Pa) tests conducted at URI. This was evident in the friction angle data and in the reloading Young's modulus data.

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Marine Georesources and Geotechnology