This paper presents the results of physical modelling tests carried out on a geotechnical centrifuge to investigate the influence of an embankment load on the behaviour of a pipeline buried in clayey soil. A series of centrifuge tests was performed on a pipeline model buried in a kaolin–sand soil mixture to model the behaviour of a pipeline crossing below an embankment. The embankment was modelled using unsaturated sand layers built above the kaolin–sand soil. The test set-up allowed the acquisition of both deformations corresponding to the longitudinal bending, and forces developed on the pipe during the consolidation of the soil due to the application of the embankment layers. The influence of pipe embedment was also investigated through tests with different soil heights above the pipe crest. The results indicated that the force transmitted to the pipeline comprises two components: a force due to the self-weight of the soil above the pipe and a force developed owing to soil settlement during the consolidation phase. The force component due to the self-weight of the soil decreased with depth, whereas the force component due to consolidation remained nearly constant. Test results were compared with results obtained from different analytical approaches documented in the literature to understand the behaviour of buried pipelines under similar loading conditions.
This paper presents the results of physical modelling tests carried out on a geotechnical centrifuge to investigate the influence of a soil mass movement on the behavior of a pipeline buried in a marine soil. In this study, a series of centrifuge tests was performed on a model pipeline buried in Roncador oil field marine clay. The soil mass movement was modelled using a vertical plate that pushed the soil towards the pipe. The test setup allowed the measurement of deformations and forces developed in the pipe during the consolidation of the soil and due to the soil movement. The influence of pipe embedment was also investigated through different tests with different soil heights above the pipe crest. The results indicate that the force transmitted to the pipeline decreases with the increase of the pipe freedom to displace when subjected to the soil loading. Additionally, the force on the pipe increases as the embedment ratio increases. The tests results were compared with different analytical approaches documented in the literature in order to understand the behavior of buried pipelines under similar loading conditions and to quantify the stresses and deformations, which are considered key inputs for any design procedure.
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.
Soil stabilization by compaction plays an important role in foundation engineering, both for construction and maintenance. Compaction specifications often require achievement of an in situ dry density (ρd) of 90–95% of the maximum value obtained from laboratory standard or modified Proctor test. However, ρd is not a design parameter per se; it is rather used to infer other parameters such as strength and stiffness through some empirical relationships. This paper describes a setup and procedure by which the small-strain (dynamic) shear stiffness can be measured accurately by propagating elastic shear wave through the stabilized material during laboratory compaction. The method enables measurement of the shear modulus [Go(ij)] in both horizontal and vertical planes. The ratio between Go in these two orthogonal planes (i.e., Ghh and Ghv) is a measure of the degree of stiffness anisotropy, and this could be used as input parameter in deformation calculations. The setup is designed so that it can be readily incorporated into the familiar Proctor test.
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