Physical and Numerical Modeling of Dynamic Penetration of Ship Anchor in Clay

Abstract

The drop/drag process of ship anchors poses a severe threat to the underwater facilities lying on or embedded within the seabed/riverbed. To investigate the penetration depth of ship anchors within clayey seabed under emergent dropping conditions, physical and numerical simulations were performed in this study. The model tests were conducted at 1g condition, and the anchor acceleration was measured by an accelerometer sealed in the model anchor. By integrating the measured acceleration, the velocity and penetration depth during the dynamic penetration of the ship anchor in seabed can be determined. Subsequently, three-dimensional large deformation finite-element (3D LDFE) analyses using the coupled Eulerian-Lagrangian (CEL) approach were performed to investigate the anchor penetration depth in rate-dependent uniform clay. The effects of the strain-rate parameter, reference strain-rate, soil undrained shear strength, impact velocity, and anchor mass on the final penetration depth of the anchor were investigated. An analytical model was then established to predict the motion history of the anchor during its dynamic penetration process within seabed. In the analytical model, each force acting on the ship anchor was thoroughly discussed. Finally, an empirical formula in terms of the anchor total energy was put forward for the convenience of quickly predicting the anchor penetration depth in soft clayey seabed.