ABSTRACT:

We simulate behavior of salt-basin sediments using a constitutive formulation that incorporates stress-level dependency and compare the results to those from a constant-friction-angle material model. Specifically, we simulate sediment behavior with SR3KH, a critical state model developed from recent experimental work on highly smectitic Gulf of Mexico mudrocks. These experimental data demonstrate a friction angle decrease and a uniaxial stress ratio increase with increasing confining stress levels. We find that stress-level dependency predicts a more uniform stress state near salt, because of the increasing stress ratio. At the same time, however, sediments are weaker and closer to failure, because the slope of the critical state line decreases and sediments fail at a lower ratio of shear to mean effective stress. Overall, incorporating this fundamentally different material behavior into sediment description is the first step towards simulating sediment response at the high stress levels and under the complex stress paths that characterize geologic systems.

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