基于饱和海洋黏土流固耦合方法的张紧式组合吸力锚承载特性研究

The exploration and utilization of ocean resources are moving toward deep-water zones, which is the key strategy of China’s sea development. Therefore, techniques of deep-water platforms are highly required in China’s seas. Considering the taut mooring system of deep-water floating platforms, a group of conjoined taut suction anchors typically arranged as a triangle in the plane layout is studied in this project. Based on the novel mesoscopic CFD-DEM approach developed by the applicant, in this project, the new DEM contact model for marine clay and CFD-DEM model describing the accumulation and dissipation of pore water pressure in saturated clay will be developed and further used to simulate the performance of the conjoined taut suction anchors in soft marine clay. With the help of the newly developed CFD-DEM coupling model combining with the geotechnical centrifugal test and upper plastic limit analysis, the mesoscopic deformation of ground soil, failure modes and bearing capacity of the conjoined suction anchors will be fully studied, considering loading conditions of taut mooring system, properties of soft clay in deep-water zones in South China Sea and anchor layout. The joint working mechanism and effect of multiple-anchor foundation can be further understood. Finally, a practical analytical solution of bearing capacity of the conjoined taut suction anchors will be proposed and this will provide useful guidelines and be further applied in the design and assessment of deep-water floating platforms.

海洋资源的开发和利用逐步向深远海迈进，这已成为我国海洋发展战略的关键。因地制宜地发展适应我国海况的深海平台技术迫在眉睫。针对深水浮式平台张紧式系泊系统锚固型式，本项目对典型的平面布置呈三角形的多个吸力锚组合基础承载特性开展研究。在新兴的离散元与计算流体动力学细观流固耦合方法(CFD-DEM)基础上，进一步开发适用于海洋黏土的离散元模型、以及考虑饱和黏土孔压累积与消散的流固耦合模型，以此模拟吸力锚基础服役过程；并联合运用土工离心机模型试验、塑性上限理论分析等手段，结合张紧式锚固基础受力特点，针对我国南海深水区软黏土力学特性，考虑土体强度、加载条件、锚尺寸与空间布置、单锚失效等多种影响因素，对循环荷载作用下地基土的细观变形演变过程、锚基础的破坏模式和承载力进行研究，揭示多锚组合基础的群锚效应和联合工作机理；建立组合锚基础循环承载力实用理论计算方法，为深水平台锚固基础的设计和评价提供理论依据。

海洋资源的开发及利用在近海区域已逐渐成熟，深海资源的开发和利用迫在眉睫。针对深水浮式平台张紧式系泊系统锚固型式，本项目已完成典型平面上多个吸力锚组合基础承载特性研究工作。结合南海深海区黏土土力学特性，成功开发适用于南海饱和海洋黏土的离散元数值模型，并通过固结试验及动三轴试验进行验证；采用流固耦合数值模拟方法，捕捉考虑饱和海洋黏土桩土作用下的孔压分布及土体演化规律，探究了张紧式组合吸力锚的破坏机制及承载特性；采用离心机试验开展多组张紧式组合吸力锚，考虑土体强度、加载条件、锚尺寸与空间布置、单锚失效等多种影响因素，揭示多锚组合基础的群锚效应和联合工作机理；利用塑性上限分析理论建立循环荷载作用下组合锚基础极限承载力计算方法，可对吸力锚基础进行了全过程使用周期计算及设计提供指导。依托本项目研究成果，发表期刊论文15篇，授权专利6项、软著2项，指导博士2名，硕士7名。