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Numerical modeling of drag anchors of floating structures - comparison of ultimate holding capacity with limit equilibrium methods

Meyer, V. (ed.), Frontiers in Offshore Geotechnics III: proceedings of the Third International Symposium on Frontiers in Offshore Geotechnics (ISFOG 2015), Oslo, Norway, 10-12 June 2015, CRC Press, Boca Raton, pp. 857-862.

10 Jun 2015
Viana da Fonseca, V. and Dias, H.
DOI: 10.1201/b18442-122

This work is focused on the determination of the Ultimate Holding Capacity (UHC) of a model of a drag anchor for wave energy conversion prototype structures, installed in sandy seabed soils in Portuguese Atlantic continental western coast. It also studies the evolution of the installed stresses in the soil mass mobilized by the movement imposed to the anchor. In order to determine the UHC, different methods were used: empirical (NCEL), limit equilibrium and numerical model (using the commercial code Plaxis®). Nine case studies were defined, proceeding to the application of the different methods. The construction of the numerical model using the referred software required the admission of geomechanical parameters determined from results of triaxial tests on representative sandy samples, for the adopted Hardening Soil Model (HSM). On the numerical modeling, a simple routine was developed in which the load applied on the anchor increased progressively. Results are discussed, in the view of a comparison between empirical methods, such as the NCEL and the ones given by a manufacturer, as well as the Neubecker & Randolph and the LeLievre & Tabatabaee limit state methods. The application of the Plaxis-2D program converged quite well when considering the soil volume that followed the movement imposed to the anchor.


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