Centrifugal model tests and numerical simulations of dragging motion state of Hall anchor

For the submarine pipelines and cables laid flat or shallowly buried in the seabed, the accidental anchor dragging operation is one of the important factors affecting their safe operation. Due to the large deformation and failure of soil during the dragging process of the anchor in the soil, it involves many mechanical problems such as material nonlinearity, geometric nonlinearity and contact nonlinearity. It is difficult to accurately analyze the dragging process through the analytical research methods. In this paper, the centrifugal model tests and numerical analysis are used to study the dragging anchor. The motion trend, the development law of drag force and the penetration depth of anchors with different weights on different types of seabed are tested and calculated. The results show that the dragging anchor in low-strength cohesive soil is likely to produce a false bottom grabbing phenomenon. For the anchors are dragged on the medium- and high-strength cohesive soil seabed, the dragging process of the anchors can be divided into three stages: soil platform formation, anchor claw wedge and motion stability. On the non-cohesive soil and cohesive soil seabeds, the drag distance at the stability stage is 4 and 1.27 ~ 1.96 times the anchor length, respectively. For the Hall anchor with the weight greater than 6 t, whether on the cohesive soil seabed or the non-cohesive soil seabed, the penetration depth of the anchor claw is greater than 1 m, and the dragging operation is likely to cause direct damage to the submarine pipelines or cables, which needs attention.