波浪荷载与海底土层渗流耦合作用下桩基承载性能研究

Bearing capacity and stability of the seabed and underwater pile foundation is an important subject of the marine engineering geology. The impact of wave-induced seabed seepage on the pile-soil interface behavior is a key topic in evaluating the bearing performance of offshore piles. In past researches, the difference of interface behavior under seepage influence and stress driving is not discussed. In order to study the interface behavior driven by the stress, seepage and their coupling effect, the nonlinear coupling progress of pile-soil-underground water-wave should be resolved. For the construction of ocean engineering structures and the marine engineering geology investigation, it is significant to clarify the bearing mechanism of piles in saturated seabed under wave loading. In this research, the nonlinear coupling progress of wave-saturated seabed-pile will be studied by model tests and numerical analysis, and the bearing performance of piles in paralic environment can been obtained. The interactive behavior on the pile-soil interface impacted by the coupling effect of seepage and stress is analyzed the interface shearing tests to get a new constitutive model and its parameters. After simulating the offshore wave loading in a numerical method, the wave-induced response of saturated seabed is studied to obtained the stress and pore water pressure field in the seabed. Then the interactive mechanism of wave-underground water-seabed soil-pile foundation can be investigated numerically by employing the new interface model which has considered the effect of seepage driving. The interactive behavior between pile and saturated soil under the wave load is also measured by the lab model tests with a modified testing system. Based on the results of model tests and nonlinear coupling numerical analysis, the response mechanism of piles under the difference condition of the coupling effect between wave and seabed seepage would been obtained, and the evaluation method of pile's bearing performance influenced by the soil seepage field can be presented. The results and conclusions of this research will provide a theoretical and technical support for the safety control of ocean resource development and prevention of the marine engineering geology disaster.

海床地基和桩基的承载力与稳定性是海洋工程地质评价的重要内容，波浪作用下海床渗流对桩土界面力学特性的影响是评价海洋工程桩基性能的关键，现有研究均未能区分渗流与应力作用下桩土界面力学响应的差异。研究渗流、应力及其耦合驱动下的桩土界面特性，涉及结构-土颗粒-地下水-波浪相互作用的高度非线性多场耦合问题。揭示波浪荷载下饱和海床中桩基承载机理，对于海洋工程建设及海域工程地质调查具有重要意义。本项目采用室内试验和耦合理论分析，研究近海环境中桩基的承载性能。通过接触面试验，分析土层应力与渗流非线性耦合作用的桩土界面行为特征，建立本构模型；结合饱和海床的应力渗流响应机制研究，探讨波浪-地下水-土层-桩基的相互作用规律；综合模型试验和非线性耦合分析，揭示波浪荷载和海底土层渗流不同作用顺序下桩基响应机理，提出渗流影响下的桩基承载性能评估方法，为海洋资源开发安全保障和海洋工程地质灾害防治提供理论依据和技术支撑。

海床地基和海洋桩基的承载力与稳定性分析是海洋工程地质评价的重要内容。海洋环境与海底地质条件复杂，波浪引起的饱和海床孔压响应与波浪荷载的耦合作用对海床与结构物的影响不容忽视。揭示波浪荷载下饱和海床中桩基承载机理，对于海洋工程建设及海域工程地质调查具有重要意义。本项目采用室内试验和耦合理论分析，以饱和海床孔压响应、桩土相互作用为切入点，研究了近海浅水环境中波浪荷载作用下的桩基的响应特征与承载性能。. 1、研制一维波浪加载的单桩海床模拟试验装置，实现对波浪荷载作用下饱和海床孔压响应、桩身应变与位移的实时测试。通过室内试验，研究了波浪作用下桩周土的孔压响应，阐明海床孔压响应的相位延迟和振幅衰减作用，揭示了桩基对海床孔压响应与渗流效应的影响机理。. 2、提出了波浪作用下海底单桩动力响应的准静态数值分析方法，采用准静态方法模拟波浪荷载，考虑桩土界面的非线性接触面特性，分别研究了完全埋置桩、海洋桩柱及饱和海床的响应。分析结果阐明了桩土接触效应对海床孔压响应与桩身轴力变形的影响机理，分析了不同参数对桩基承载性能的影响规律。. 3、提出了包含波浪、海床和单桩的三维数值模拟方法研究其相互作用，其中波浪-桩基和桩基-海床子模型在水土交界面上实现耦合，同时考虑基于Biot理论的饱和海床渗流和桩身振动效应。研究了振动作用下海床孔压、液化以及单桩位移、弯矩等响应，并对波浪、海床土体和单桩等主要参数影响进行了分析。. 4、提出了基于瞬时剪应力的三维累计孔压模型，通过海床土孔压的非线性累积响应探讨桩土相互作用的长期效应。该三维模型可以较为准确地模拟含单桩海床的累积孔压响应，并可反映累计孔压会振动上升的特征。分析揭示了桩周剪应力集中导致孔压累计强化和液化加剧的作用机制。. 本项目研究成果发表论文21篇（其中SCI检索17篇），并录用4篇SCI期刊论文和1篇中文论文；授权发明专利6项，申请发明专利2项；培养博士生1人、硕士生4人。