Strength Behaviour Analysis of an Offshore Brazilian Marine Clay

The main purpose of this paper is to describe the geotechnical behaviour of a deep water marine clay obtained from Campos basin oil field located offshore the state of Rio de Janeiro in Brazil. The soil samples were obtained at a depth of about 1500 m using a Kullenberg piston corer. Characterization tests were undertaken on the clay samples, including water content, Atterberg limits, particle size distribution and specific density. Isotropic and anisotropic undrained triaxial tests were also carried out on both normal and over-consolidated samples to assess both the conventional strength and Cam-clay parameters. Additionally, oedometer tests were performed to evaluate the compressibility of both undisturbed and reconstituted soil samples. Finally, a series of T-bar penetrometer tests were performed on the mini-drum geotechnical centrifuge at COPPE, the University of Rio de Janeiro to establish the undrained shear strength profile. The results obtained from the T-bar tests were compared with the theoretical strength curves that were established based on the Cam-clay parameters derived from the laboratory tests. The results obtained in this study indicated a useful methodology to assess and capture the behaviour of marine clay. The assessment of strength behaviour of marine clay is quite essential in modelling of wide range of soil-offshore structure interaction problems such as pipelines, mudmats and anchors.