Numerical simulation of the penetration process of ship anchors in sand

Abstract

In order to study the burial depth of submarine power cables in the German North Sea, the penetration process of ships' anchors in seabed soil was simulated by using the coupled Eulerian–Lagrangian method in Abaqus/Explicit. In the 3D finite element model the sandy seabed was simulated with different densities under both drained and undrained conditions. The resulting penetration mechanism of a ship anchor in sand was verified by field test data. It showed that under specific conditions the penetration depth of a ship's anchor could be more than 1.5 m, which is suggested in “Bundesfachplan Offshore für die deutsche ausschließliche Wirtschaftszone der Nordsee 2012 und Umweltbericht” [8] as the standard burial depth of submarine power cables in the German North Sea by Bundesamt für Seeschifffahrt und Hydrographie (BSH).Numerische Simulation des Penetrationsprozesses eines Schiffsankers in Sand. Um die Verlegetiefe von Offshore‐Seekabeln in der Nordsee zu untersuchen, wurde der Penetrationsprozess eines Schiffsankers in den Meeresboden mittels der gekoppelten Euler‐Lagrangeschen Methode im Abaqus/Explicit modelliert. Im 3D‐FE‐Modell wird der sandige Meeresboden mit unterschiedlichen Lagerungsdichten unter dränierten sowie undränierten Bedingungen angesetzt. Der berechnete Eindringmechanismus des Schiffsankers im Sand wird durch Feldmessungen in der Nordsee bestätigt. Es zeigt sich, dass die Penetrationstiefe des Ankers unter Umständen größer ist als die im “Bundesfachplan Offshore für die deutsche ausschließliche Wirtschaftszone der Nordsee 2012 und Umweltbericht” [8] vom Bundesamt für Seeschifffahrt und Hydrographie (BSH) vorgegebene Verlegetiefe von 1,5 m.

Impact on submarine cables due to ship anchor – soil interaction

“…This depth, namely the maximum fluke depth, is important for the risk of damage to a submarine cable. Grabe et al [9] observed in numerical simulations and field tests (see also [4]) three varying penetration depths, which have to be differentiated. Fig.…”

“…Ivanovic et al simulated the penetration of fishing gear into the subsoil using a three‐dimensional FE model with adaptive remeshing technique. Grabe et al and Grabe and Wu modelled the penetration process of anchors in sand and clay using a CEL approach that is described below.…”

“…A CEL model was used to simulate the penetration process of ship anchors in sand . Drained and undrained conditions of the soil were considered.…”

“…To validate the numerical simulations, a comparison with field tests was conducted, which shows that the results of the numerical model used were appropriate. Grabe et al divided the penetration process of the anchor in sand into four stages. The first stage includes the start of anchor penetration into the subsoil due to self‐weight.…”

Large displacement numerical study of 3D plate anchors

“…Since the large soil-plate displacements cannot be captured with the standard Lagrangian FEM because of issues with element distortions, Arbitrary Lagrangian-Eulerian methods (ALE) and particle-based methods have been developed in the last few decades (Atluri & Zhu, 2000;Donea & Huerta, 2004). Among them, the remeshing and interpolation technique with small strain (RITSS) method (Hu & Randolph, 1998), the coupled Eulerian-Lagrangian (CEL) method (Grabe, Qiu, & Wu, 2015;Qiu, Henke, & Grabe, 2011), and the Material Point Method (MPM) (Sulsky, Chen, & Schreyer, 1994) have been successfully applied in soil penetration problems similar to the anchor pull out discussed in this paper Mahmoodzadeh & Randolph, 2014;Phuong, van Tol, Elkadi, & Rohe, 2016;Tian, Cassidy, Randolph, Wang, & Gaudin, 2014).…”