Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study o...Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study of drag anchors. The techniques for measuring the trajectory and movement direction of drag anchors in soils, the techniques for measuring the moving embedment point and reverse eatenary shape of the embedded drag line, the penetration mechanism and kinematic behavior of drag anchors, the ultimate embedment depth of drag anchors, the movement direction of the anchor with an arbitrary fluke section, the reverse catenary properties of the embedded drag line, the interaetional properties between drag anchor and installation line, the kinematic model of drag anchors in seabed soils, and the analytical method for predicting the anchor trajectory in soils will all be examined. The present work remarkably reduces the uncertainties in design and analysis of drag embedment plate anchors, and is beneficial to improving the application of this new type of drag anchor in offshore engineering.展开更多
综合调研现有海上浮式风机的种类、特征和系泊锚的基本情况,对于现有浮式风机常用的吸力锚、拖曳锚、重力锚在实际工程中的应用、设计施工考虑要点、优势与局限性进行分析。结果表明,深吃水立柱式(Spar)结构配吸力锚、半潜式结构配拖曳...综合调研现有海上浮式风机的种类、特征和系泊锚的基本情况,对于现有浮式风机常用的吸力锚、拖曳锚、重力锚在实际工程中的应用、设计施工考虑要点、优势与局限性进行分析。结果表明,深吃水立柱式(Spar)结构配吸力锚、半潜式结构配拖曳锚、张力腿平台(Tension Leg Platform,TLP)结构配重力锚是目前常用的配套形式,其中半潜式结构配拖曳锚认可度最高。上述结果可为我国海上浮式风机系泊锚型的选取与设计提供相应的参考依据。展开更多
Positioning drag anchors in seabed soils are strongly influenced not only by the properties of the anchor and soil, but also by the characteristics of the installation line. The investigation on the previous predictio...Positioning drag anchors in seabed soils are strongly influenced not only by the properties of the anchor and soil, but also by the characteristics of the installation line. The investigation on the previous prediction methods related to anchor positioning demonstrates that the prediction of the anchor position during dragging has inevitably introduced some key and unsubstantiated hypotheses and the applicability of these methods is limited. In the present study, the interactional system between the drag anchor and installation line is firstly introduced for the analysis of anchor positioning. Based on the two mechanical models for embedded lines and drag anchors, the positioning equations for drag anchors have been derived both for cohesive and noncohesive soils. Since the drag angle at the shackle is the most important parameter in the positioning equations, a novel analytical method that can predict both the variation and the exact value of the drag angle at the shackle is proposed. The analytical method for positioning drag anchors which combines the interactional system between the drag anchor and the installation line has provided a reasonable theoretic approach to investigate the anchor behaviors in soils. By comparing with the model flume experiments, the sensitivity, effectiveness and veracity of the positioning method are well verified.展开更多
Drag anchor is one of the most commonly used anchorage foundation types. The prediction of embedded trajectory in the process of drag anchor installation is of great importance to the safety design of mooring system. ...Drag anchor is one of the most commonly used anchorage foundation types. The prediction of embedded trajectory in the process of drag anchor installation is of great importance to the safety design of mooring system. In this paper, the ultimate anchor holding capacity in the seabed soil is calculated through the established finite element model, and then the embedded motion trajectory is predicted applying the incremental calculation method. Firstly, the drag anchor initial embedded depth and inclination angle are assumed, which are regarded as the start embedded point. Secondly, in each incremental step, the incremental displacement of drag anchor is added along the parallel direction of anchor plate, so the displacement increment of drag anchor in the horizontal and vertical directions can be calculated. Thirdly, the finite element model of anchor is established considering the seabed soil and anchor interaction, and the ultimate drag anchor holding capacity at new position can be obtained. Fourthly, the angle between inverse catenary mooring line and horizontal plane at the attachment point at this increment step can be calculated through the inverse catenary equation. Finally, the incremental step is ended until the angle of drag anchor and seabed soil is zero as the ultimate embedded state condition, thus, the whole embedded trajectory of drag anchor is obtained. Meanwhile, the influences of initial parameter changes on the embedded trajectory are considered. Based on the proposed method, the prediction of drag anchor trajectory and the holding capacity of mooring position system can be provided.展开更多
基金Foundation item： Supported by the National Natural Science Foundation of China （Grant nos. 50639030 and 50979070） and the 863 Program of China （Grant no. 2006AA09Z348）.
文摘Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study of drag anchors. The techniques for measuring the trajectory and movement direction of drag anchors in soils, the techniques for measuring the moving embedment point and reverse eatenary shape of the embedded drag line, the penetration mechanism and kinematic behavior of drag anchors, the ultimate embedment depth of drag anchors, the movement direction of the anchor with an arbitrary fluke section, the reverse catenary properties of the embedded drag line, the interaetional properties between drag anchor and installation line, the kinematic model of drag anchors in seabed soils, and the analytical method for predicting the anchor trajectory in soils will all be examined. The present work remarkably reduces the uncertainties in design and analysis of drag embedment plate anchors, and is beneficial to improving the application of this new type of drag anchor in offshore engineering.
文摘综合调研现有海上浮式风机的种类、特征和系泊锚的基本情况,对于现有浮式风机常用的吸力锚、拖曳锚、重力锚在实际工程中的应用、设计施工考虑要点、优势与局限性进行分析。结果表明,深吃水立柱式(Spar)结构配吸力锚、半潜式结构配拖曳锚、张力腿平台(Tension Leg Platform,TLP)结构配重力锚是目前常用的配套形式,其中半潜式结构配拖曳锚认可度最高。上述结果可为我国海上浮式风机系泊锚型的选取与设计提供相应的参考依据。
基金financially supported by the National Basic Research Program of China(973 Program,Grant No.2009CB219507)the National Natural Science Foundation of China(Grant Nos.50639030 and 50979070)the National Science and Technology Major Project of China(Grant Nos.2011ZX05056-002 and 2011ZX05026-004)
文摘Positioning drag anchors in seabed soils are strongly influenced not only by the properties of the anchor and soil, but also by the characteristics of the installation line. The investigation on the previous prediction methods related to anchor positioning demonstrates that the prediction of the anchor position during dragging has inevitably introduced some key and unsubstantiated hypotheses and the applicability of these methods is limited. In the present study, the interactional system between the drag anchor and installation line is firstly introduced for the analysis of anchor positioning. Based on the two mechanical models for embedded lines and drag anchors, the positioning equations for drag anchors have been derived both for cohesive and noncohesive soils. Since the drag angle at the shackle is the most important parameter in the positioning equations, a novel analytical method that can predict both the variation and the exact value of the drag angle at the shackle is proposed. The analytical method for positioning drag anchors which combines the interactional system between the drag anchor and the installation line has provided a reasonable theoretic approach to investigate the anchor behaviors in soils. By comparing with the model flume experiments, the sensitivity, effectiveness and veracity of the positioning method are well verified.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51890915,51490672,and51761135011)the Fundamental Research Funds for the Central Universities
文摘Drag anchor is one of the most commonly used anchorage foundation types. The prediction of embedded trajectory in the process of drag anchor installation is of great importance to the safety design of mooring system. In this paper, the ultimate anchor holding capacity in the seabed soil is calculated through the established finite element model, and then the embedded motion trajectory is predicted applying the incremental calculation method. Firstly, the drag anchor initial embedded depth and inclination angle are assumed, which are regarded as the start embedded point. Secondly, in each incremental step, the incremental displacement of drag anchor is added along the parallel direction of anchor plate, so the displacement increment of drag anchor in the horizontal and vertical directions can be calculated. Thirdly, the finite element model of anchor is established considering the seabed soil and anchor interaction, and the ultimate drag anchor holding capacity at new position can be obtained. Fourthly, the angle between inverse catenary mooring line and horizontal plane at the attachment point at this increment step can be calculated through the inverse catenary equation. Finally, the incremental step is ended until the angle of drag anchor and seabed soil is zero as the ultimate embedded state condition, thus, the whole embedded trajectory of drag anchor is obtained. Meanwhile, the influences of initial parameter changes on the embedded trajectory are considered. Based on the proposed method, the prediction of drag anchor trajectory and the holding capacity of mooring position system can be provided.
