Numerical analysis of torpedo anchors

This paper presents the development of a numerical framework based on the finite element method and its application in the analysis of torpedo anchors. The procedure is based on a mixture theory for the dynamic behaviour of saturated porous media. The nonlinear behaviour of the solid phase of soil is represented by the Modified Cam Clay material model and the interface between the soil and the structure is modelled by a mortar segment-to-segment frictional contact method. An Arbitrary Lagrangian-Eulerian (ALE) method is adopted to avoid mesh distortion throughout the numerical simulation. The generalised-α method is utilised to integrate the governing equations of motion in the time domain. Results obtained from the installation phase of a torpedo anchor reveal that the anchor decelerates at a constant rate during most of its penetration. Analysis results show a typical distribution of excess pore-water pressure during free falling installation, having higher magnitudes at the face and lower magnitudes along the shaft. The computational results for the setup phase indicate that for soil elements located within a radial distance of approximately one diameter from the centreline of the torpedo, 90% of consolidation takes place in a few days after installation, depending on the value of soil permeability.