波浪诱发缓坡滑动作用下海洋桩基的变形机理研究

Performance and safety of the offshore pile foundation is one of the important subject in the field of marine geotechnical engineering. In the coastal area, the long-term wave loads would cause movements of the seabed with slight slope (less than 15°). Therefore, the piles in such condition will be not only effected by the complex environmental loads, but also impacted by the wave-caused seabed movements. The mechanism of this problem is very complex and few research works has been reported. Investigation on the pile responses under the coupling of waves and seabed movements is significative for the construction and safety of ocean engineering. In this research, the nonlinear coupling mechanism of wave-caused seabed movements on slight slope and its impact on pile performance will be studied by model tests and numerical analysis. The transportation of the wave effected by the slight slope and offshore piles will be investigated by the flume experiments and numerical analysis, so that the flow field model can be obtained by hydrodynamic modelling. The deformation mechanism of the soil seabed with slight slope under wave loading can be revealed to get the slip field and it action on piles. Both conventional model tests and centrifuge model tests are carried to study the nonlinear interactive behavior of wave-slope-pile-soil. By employing the flow field of sea water and movement field of slope, the pile-multiphase flow-seabed soil interaction can be analyzed numerically. The multi-field coupling mechanism of the marine pile response can then be discovered, and evaluation method will be presented. The results and conclusions of this research will provide a theoretical support for the safety control of ocean resource development and prevention of the marine engineering disaster.

海洋桩基工作性能及安全保障是海洋岩土工程领域的重要课题。位于近海缓坡（≤15度）海床的桩基，除承受复杂环境荷载和结构工作荷载外，也会受到波浪长期作用所致缓坡滑移的影响。波浪诱发海底缓坡滑移对海洋桩基的影响是一个具有动边界效应的多相多场耦合问题，其作用机制十分复杂。本项目采用模型试验、理论分析和数值模拟等方法，研究波浪诱发海底缓坡滑移机理及其对海洋桩基的影响。通过水槽试验与数值模拟，掌握缓坡反射破碎和桩周湍流作用下的波浪传播特性，建立其水动力学模型；揭示土质缓坡海床在波浪作用下的变形机理，实现其滑移响应的位移场模拟；在桩土相互作用模型试验和离心试验的基础上，将波浪流场和缓坡滑移场引入桩基-多相流-海床土的非线性相互作用分析，揭示海洋桩基变形响应的多相多场耦合机制，阐明不同因素的影响规律，提出相应的分析评估方法。研究成果将为海洋资源开发和海洋工程建设的安全评价及灾害防治提供理论依据。

波浪作用下，缓坡海床内超静孔压响应及其导致的液化过程对海床的稳定性存在显著的影响，是海洋桩基承载力与稳定性评估中关注的重要内容。揭示波浪荷载作用下缓坡海床内的超静孔压响应机理，探索其对坡体稳定性的影响规律，并阐明桩周土体响应对桩基承载力和稳定性的影响，对于海洋桩承结构的建设和运营均有重要意义。本项目综合采用一维圆筒试验、波浪水槽试验和数值耦合分析方法，对波浪荷载作用下缓坡海床超静孔压响应机理及其对桩基承载性能的影响规律进行了研究。.一、利用一维圆筒试验和波浪水槽试验，研究了波浪荷载作用下，海床超静孔压响应规律及其对桩基竖向承载力的影响规律。通过研究，揭示了波浪长期荷载作用下粉质海床超静孔压的累积过程随深度的变化规律，阐明海洋桩基的存在导致桩周海床超静孔压波动增强、桩端超静孔压增大的作用机制，揭示了波浪荷载导致桩基竖向承载力减弱的影响机理。.二、为分析缓坡滑动导致的桩土滑移和脱离过程对桩基受力变形的影响规律，提出了考虑桩土非线性接触的CFD-FEM耦合分析模型。通过分析，揭示了桩土相对滑移和脱离过程导致桩周海床土体位移增大和桩基变形加剧的作用机理。.三、采用耦合分析模型，研究了孤立波引起的饱和海床超静孔压响应过程，分析揭示了孤立波回落阶段初始海岸线附近负的波压力的产生机理及其对海床超静孔压响应的影响机制，提出了在设计中应考虑缓坡结构物抗拔承载力的建议。.四、提出了考虑桩土非线性接触、饱和海床超静孔压响应和土体弹塑性的波浪荷载作用下桩基-缓坡海床相互作用分析模型，通过对桩周土体塑性应变、超静孔压和桩基受力变形的分析，探究了缓坡坡度对桩基承载性能的影响效应。分析揭示了海床坡度的增加将导致桩基受到的不平衡土压力增大、桩周土体液化加剧、桩基内力变形增大的作用机理。.研究成果发表论文10篇（其中SCI检索6篇、EI检索3篇），录用中文EI论文2篇；授权发明专利3项，申请发明专利1项；培养博士生2人、硕士生3人。