On the behaviour of deep-ocean sediments

The behaviour of deep-ocean sediments from the North Atlantic abyssal plains is examined within the context of a recognised framework, the Sensitivity Framework, which was developed by Cotecchia & Chandler for structured terrestrial clays. The deep-ocean sediments have very high sensitivities, of the order of those of quick clays, but in volumetric compression their destructuration occurs at more moderate rates, similar to those usually found in terrestrial clays of medium sensitivities. The deep-sea sediments were retrieved using different types of sampler, which influenced greatly the strength and stiffness of the different samples. In particular, in the lower-quality samples the greater disturbance caused by sampling is responsible for changing their behaviour from brittle to ductile during shearing after compression to stresses post-gross yield, giving them an apparent insensitivity to shear strains. Results from numerical analyses using a constitutive model that was developed for structured terrestrial clays are presented. They show that such a model, which accounts for natural structure, can be used to simulate the behaviour of deep-ocean sediments provided an appropriate destructuration law is used in the model.