霍尔锚拖曳运动状态离心模型试验与数值模拟研究

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

对于平铺或浅埋在海床中的海底管道和电缆,意外的拖锚作业是影响其安全运营的重要因素之一。由于锚在土中的拖动过程中时刻发生着土的大变形和破坏,涉及材料非线性、几何非线性及接触非线性等诸多力学问题,通过解析的研究手段很难准确地分析拖锚过程。采用离心模型试验和数值分析相结合的手段展开拖锚研究,测试和计算了不同重量的船锚在不同类型海床上的运动趋势、拖曳力发展规律、入土深度等。结果表明,在低强度的黏性土海床上拖锚,极有可能会产生一种假抓底现象;在中高强度的黏性土海床上拖锚,锚的拖动过程可以分为土台形成阶段、锚爪楔入阶段和运动稳定阶段三个阶段;在无黏性土和黏性土海床上,达到稳定阶段时拖动的距离分别是锚长的4倍和1.27~1.96倍;对于质量大于6 t的霍尔锚,无论在黏性土海床还是非黏性土海床上,锚爪的入土深度均大于1 m,拖锚作业很有可能会对海管或海缆造成直接损坏,需要引起重视。

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.