Abstract
This paper presents a new algorithmic formulation of the clay and sand pipe–soil interaction models recommended by the DNV-RP-F109 code for dynamic on-bottom stability analysis of submarine pipelines. The pipe–soil force update algorithm is formulated within the framework of computational elasto-plasticity and applies Backward-Euler integration to ensure stability and robustness for large time step sizes. Algorithmic optimization techniques are developed by utilizing a closed-form solution and subincrementation. A numerical verification study covering full cyclic displacement ranges of a 12 inch pipeline is presented. The new formulation is shown to increase the time step size by a factor of up to 50 compared to commercial software tools for on-bottom stability analysis. This achievement will be particularly beneficial for long-duration 3D nonlinear time domain on-bottom stability analysis.
Highlights
For any pipeline, umbilical, power cable or flexible a major design challenge is to ensure that the product remains on the seabed where it was installed without excessive lateral displacements
The efforts resulted in the development of the Verley and Sotberg model for sand [19,20] and the Verley and Lund model for clay [21]. These energy-based pipe–soil models form the basis for the dynamic on-bottom stability analysis recommended by the DNV-RP-F109 code, even though seabed erosion is not accounted for
The response of a short pipe section was simulated by using the SIMLA software and the 2D PONDUS software, see Table 1 and Fig. 5
Summary
Umbilical, power cable or flexible a major design challenge is to ensure that the product remains on the seabed where it was installed without excessive lateral displacements. In the case of seabed erosion [9], design guidelines such as the DNV-RP-F109 code does not offer any detailed guidance on how to predict scour-induced changes to pipeline embedment and the effect of these changes on pipeline stability [10] All of these shortcomings can be addressed by an integrated 3D analysis tool that can account for all relevant effects simultaneously in time domain. The efforts resulted in the development of the Verley and Sotberg model for sand [19,20] and the Verley and Lund model for clay [21] These energy-based pipe–soil models form the basis for the dynamic on-bottom stability analysis recommended by the DNV-RP-F109 code, even though seabed erosion is not accounted for. The PONDUS pipe–soil models for clay and sand are still regarded to represent state of the art for dynamic on-bottom stability analysis
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