系缆触底开槽效应诱发吸力锚承载力弱化机制研究

When taut or semi-taut mooring systems are used for the offshore floating wind turbines, due to its relatively shallow water depth, the environmental loads can be dynamically passed down to the embedded suction anchor by the mooring chain. Under the effects of complex and fast-changing environmental loads, strength degradation and local trench may appear within the seabed soil around the suction anchor, and thus the anchor capacity becomes obviously decreased and tends to be pulled out from the seabed. Therefore, the following studies are carried out step by step from the respects of theoretical study, numerical simulation, laboratory test and centrifuge experiment: The calculation method for the soil resistance to embedded line will be proposed and calibrated. The vector-form intrinsic FEM is used to simulate the three-dimensional dynamic interactions between suspended chain, seabed soil and sea water, and reveal the characteristics of dynamic tension loads acting on the anchor. The local trench near the touchdown zone of mooring chain is investigated through a series of pool experiments, and the inner mechanism for the trench existed on the seabed is studied, as well as its affecting factors. By combining centrifuge experiments and numerical simulations, the influences of cyclic tension and seabed trench on the failure mode of suction anchor in sandy seabed are evaluated, and then key factors for bearing capacity degradation are thoroughly studied, an assessment method is finally proposed to predict the capacity of suction anchor under cyclic loadings. The research outputs of this project can provide the necessary scientific basis for the design of anchoring foundation for floating wind turbines in China.

当张紧/半张紧式系泊系统用于近海浮式风机系泊时，由于工作水深相对较浅，复杂多变的海上环境荷载易于通过系泊缆索动态地传递至吸力锚基础承担，这将导致其周围土体出现明显弱化、开槽等现象，吸力锚的承载力显著降低，甚至可能发生拔出失效。因此，本项目拟综合利用理论研究、数值计算、室内试验及离心模型试验等手段，逐步开展以下研究：提出嵌入海床段系缆的土体抗力计算方法并标定其参数，基于向量式有限元构建系缆-海床-海水三维动力作用数值模型，分析掌握作用于典型浮式风机吸力锚基础上的动张力荷载特点；开展水池试验研究系缆在海床触地区的开槽现象，揭示系缆触底开槽效应的内在机制及其影响因素；离心模型试验结合数值计算，研究系缆的循环张拉和开槽效应对砂质海床中吸力锚失效模式的影响，分析揭示导致吸力锚承载力弱化的关键因素，最终提出吸力锚循环承载力的评价方法。本项目的研究成果可为我国海上浮式风机系泊基础设计提供必要的科学依据。

本项目的研究对象是用于海上浮式风机系泊的吸力锚基础，主要研究内容包括：沿系缆的动张力荷载传递特点、系缆在海床触地区的开槽效应和吸力锚基础抗拔承载力弱化机制。在本项目的资助下，研究团队聚焦于系缆触底开槽诱发吸力锚承载力弱化机制，开展了一系列理论研究和技术创新，重点阐明了沿悬张系缆的动张力荷载传递特点，深入揭示了系缆在海床触地区的开槽效应，建立了触地区开槽形态的预测方法，开展了考虑开槽效应的吸力锚基础承载力弱化机制研究，并创新提出了在吸力锚顶部附加盖板的优化方案，可有效降低开槽效应的影响。本项目的研究成果为我国海上浮式结构物（特别是海上浮式风机）的锚泊基础设计提供了技术支撑。.在本项目资助期间，发表学术论文28篇（均已标注本项目编号，SCI论文24篇），主编学术专著1部，授权发明专利10件（国际发明专利2件），登记软件著作权2项，获工程建设科学技术进步奖一等奖1项。项目负责人被邀担任国际智能基础设施健康监测ISHMII学会ECR委员、中国土木工程学会港口工程分会理事，担任《Sustainability》编委、《中南大学学报》（自然科学版）青年编委、《工程科学学报》青年编委。项目负责人组织国际学术会议1次、国内会议2次，应邀做学术会议报告8 次（国际3次）。培养博士生4名（毕业2名）、硕士5名（毕业4名），指导博士后1名。在资助期内圆满完成了预期研究目标。