Modelling the effects of structure in deep-ocean sediments

Abstract

Good quality data from advanced laboratory tests performed on deep-sea sediments are very rare. Most existing data were obtained from tests on remoulded or highly disturbed samples. As a consequence many unknowns remain in the behaviour of those soils, such as the effects of structure on their mechanical behaviour, and it is difficult to predict their performance for offshore engineering problems. In this paper, results from advanced laboratory triaxial tests on deep-ocean sediments from the North Atlantic abyssal plains are examined within the context of the Sensitivity Framework, which was developed by Cotecchia and Chandler (2000) to describe the behaviour of structured terrestrial clays. When applied to deep-ocean sediments the Sensitivity Framework sheds some light on the effects of structure on these soils. Despite the likely disturbance that the sediments experienced during sampling, comparison between the behaviours of "undisturbed" and reconstituted specimens of deep-sea sediments shows significant effects of structure in the intact samples, with very high sensitivities of the order of those of quick clays. However the degradation of structure during loading, also called destructuration, occurs at rates more similar to those of terrestrial clays of medium sensitivities. This paper demonstrates that a numerical model, the S3-SKH model (Baudet & Stallebrass 2004), which was developed for structured terrestrial clays and includes effects of structure and "destructuration", can be used to simulate the behaviour of deep-sea sediments. © 2005 Taylor & Francis Group.