On the Working Mechanism of Two-Phase Varying Stiffness Piled Raft Foundation

两阶段变刚度桩筏基础是“厦门市花岗岩残积土复合桩基”课题组提出的一项复合桩基新技术。通过桩顶设置变形调节装置，两阶段变刚度桩筏基础克服了天然筏板基础沉降和差异沉降过大的问题和常规端承型桩筏基础无法发挥筏板底部表层地基土承载力的问题。在沉降和差异沉降控制方面，两阶段变刚度桩筏基础与常规端承型桩筏基础相当，但是前者可充分发挥良好的地基土承载力，在满足整体安全度的前提下，显著减少桩数和筏板内力，表现出明显的优越性和经济性。 本文主要研究内容包括： （1）利用ABAQUS有限元软件建模，通过两阶段变刚度桩筏基础与天然筏板基础、常规复合桩基的对比，得到两阶段变刚度桩筏基础的“两阶段”特性。同时分别从...Two-phase varying stiffness piled raft foundation is a new technology proposed by “Xiamen granite residual soil composite pile foundation” research group. All types of existing building foundations have their own weaknesses and shortcomings. For example, the non-uniform settlement and average settlement of raft foundation are too large and the good bearing capacity of topsoil cannot be used by end...学位：工学硕士院系专业：建筑与土木工程学院_结构工程学号：2532010115170

Stability Analysis of Deep Foundation Pit of Hechang Trade Center in Quanzhou

基坑力学特性与变形机理复杂，且具有较强地域性，在进行基坑支护设计及施工时多采用工程经验类比法，为确保基坑的稳定性，需要对基坑稳定性进行较为详细的分析验证。本文针对泉州和昌贸易中心大型深基坑工程，在总结基坑稳定性分析基本原理及验算公式的基础上，进行整体、抗隆起、抗倾覆及抗冲剪稳定性分析验算，得到基坑四种稳定性安全系数，以验证此基坑的稳定性，在此基础上，深入探讨了土层粘聚力、内摩擦角及重度和桩入土深度等因素与基坑四种稳定性安全系数的相互关系，对于基坑工程的稳定性分析具有一定参考意义。本文主要研究结论包括： （1）本基坑整体稳定性安全系数为2.362，满足规范要求。基坑整体稳定性安全系数随土层内摩...The mechanical characteristics and deformation mechanism of foundation pit is complex, and have strong regional characteristics, so the engineering experience analogy is always used in supporting design and construction of foundation pit. To eguarantee the stability, detailed analysis on the foundation pit’s stability is needed. Aimed at large deep foundation pit engineering of Hechang Trading Cen...学位：工程硕士院系专业：建筑与土木工程学院_工程硕士(建筑与土木工程)学号：2532012115170

Supporting construction monitoring and deformation control study of large and deep foundation pit

深基坑工程大多处于城市中心，为确保深基坑稳定及保护周边环境，需要对支护结构和周边土体的变形进行控制。本文以泉州和昌贸易中心深基坑工程为背景，对支护结构和周边土体的变形控制展开研究。通过对实测数据进行分析，总结围护桩水平位移、支撑梁钢筋应力、立柱竖向位移、坡顶变形、地表沉降、建筑物沉降、地下管线沉降、土压力及水位的变化规律，并对深基坑的稳定性与变形作出评价；对比Logistic曲线、Gompertz曲线、Usher曲线及分段时效曲线后选用合适的预测模型对基坑变形进行预测，有效指导施工，并探讨深基坑变形控制措施；采用FLAC3D对基坑开挖支护过程进行三维模拟，根据计算结果对围护桩变形、土体变形、支...The deep foundation pit is mostly in the center of the city. In order to ensure the stability of the deep foundation pit and protect the surrounding environment, it is necessary to control the deformation of the supporting structure and surrounding soil. In this paper, based on the deep foundation pit engineering of Hechang Trading Center in Quanzhou, the deformation control of supporting structur...学位：工程硕士院系专业：建筑与土木工程学院_工程硕士(建筑与土木工程)学号：2532014115179

The Application Research of Composite Foundation With Deformation-Coordinating Devices at the top of Pile

桩顶设置变形调节装置的复合桩基是“厦门市花岗岩残积土复合桩基”课题组提出的一项复合桩基新技术。本文在总结前人研究的基础上，深入研究了桩顶带变形调节装置的复合桩基沉降控制设计方法，该方法利用桩顶变形调节装置，使建筑物的差异沉降得到较好的控制，平均沉降和整体承载力满足规范的要求，且降低基础工程的造价。主要研究内容包括： ①在国内外复合桩基研究的基础上，深入研究了复合桩基沉降控制优化设计方法，为复合桩基差异沉降控制的模拟计算做铺垫。 ②分析了桩顶设置变形调节装置的原理、设计及其应用领域。按照两阶段变刚度设计方法，应用Plaxis有限元软件分析两阶段变刚度的工作机理。端承桩桩顶安装变形调节器，可解...Composite pile foundation with deformation-coordinating device at the top of pile is a new technology come up by the research group of Xiamen granite residual soil composite pile foundation. Based on the former researches, the Balanced Settlement Optimum Design Method is presented in this paper. Using deformation-coordinating device at the top of pile, the differential subsidence can be better red...学位：工学硕士院系专业：建筑与土木工程学院土木工程系_防灾减灾工程及防护工程学号：2532008115181

桩–土动力相互作用问题中桩身刚度的影响效应研究

通过开展2类刚度差异较大的桩基础的离心机动力模型试验,系统地讨论柔性桩和刚性桩的地震反应差异,以及周围土体对桩体的不同作用效应。对于柔性桩,周围土体的作用主要体现在对桩的约束效应上;然而对于刚性桩,土体更大程度上对桩体施加附加惯性力的作用,以致桩筏基础的周期明显高于无土时的周期;针对柔性桩和刚性桩显著的地震反应差异,巧妙地提出用桩筏结构自振频率wp r界定两者的行为,可为今后类似研究提供参考

Selection and Design of Wind Turbine Foundation for an Offshore Wind Farm

[Introduction] From 2022, the state subsidies for offshore wind power has been fully withdrawn. The foundation of offshore wind turbines is the supporting structure of wind turbines and plays a crucial role in the safe operation of offshore wind farms. Reasonable selection and design of the offshore wind turbine foundation is an effective way to reduce costs and increase efficiency of offshore wind farms under the guidance of such policies as the "30·60" dual-carbon target and the national "14th Five-Year Plan" energy plan. [Method] The article took the selection and design of a wind turbine foundation for a certain offshore wind farm as an example, and combined the construction experience of domestic offshore wind farms to compare and select the foundation types; firstly, preliminary selection was made among three foundation types, namely monopile foundation, jacket foundation and high pile cap foundation; then, combined with the marine hydrological and geological conditions of the offshore wind farm, the applicable water depths and advantages and disadvantages of different wind turbine foundation types were analyzed, and a comprehensive comparison was conducted from the aspects of structural safety, construction feasibility, duration and engineering economy. [Result] Research has shown that the selection of wind turbine foundation type is related to several factors such as water depth, soil geological conditions, natural frequency of wind turbines, capacity of construction and equipment installation, construction duration, and engineering cost. The monopile foundation has excellent structural type, construction feasibility, the shortest construction duration and the best economy. [Conclusion] The monopile foundation is recommended for the wind turbine foundation of this offshore wind farm

Research on Ground Reinforcement Technology of Offshore Wind Power Monopile Foundation

[Introduction] Under the guidance of energy policy with the goal of "double carbon", offshore wind power generation, as a new energy technology, has been widely applied and rapidly developed in China. Monopile foundation is the most economical and widely used foundation in offshore wind power. In order to solve the problem of deformation and erosion protection of monopile foundation, a foundation reinforcement technology is proposed, and the reinforcement technology is studied and analyzed, and the basis of reinforcement method is given. [Method] Researched and demonstrated the method of pile foundation reinforcement technology, selected a foundation reinforcement technology suitable for offshore construction through research on the technology roadmap and process of reinforcement, and used numerical analysis method to conduct a detailed analysis of the reinforcement effect and reinforcement influence range. [Result] The results show that under 1.15 times of load, the horizontal bearing capacity of monopile foundation strengthened by foundation can be increased by more than 15%, and it can be applied to larger capacity models through foundation reinforcement. In this analysis case, when the depth and horizontal range of foundation reinforcement reach 8 m, the benefits obtained from the soil in the direction of reinforcement depth are greater than those in the direction of reinforcement plane. [Conclusion] The technical scheme of using cement soil reinforcement has been verified to be reliable through numerical analysis, significantly improving the bearing capacity of monopile, and the reinforcement range is reasonable and economical. It can provide reference for the application of monopile foundation reinforcement technology in subsequent offshore wind power engineering

桩筏基础–土动力相互作用的离心机模型试验研究

通过开展离心机动力模型试验,深刻地揭示桩筏基础与土之间的动力相互作用将造成基础和土体运动的非一致性,土体的运动不能代表基础的运动,两者在加速度时程、反应谱特征、共振周期等方面均存在显著的差异,传统结构抗震设计中采用自由场土体的动力参数直接作为基础的动力参数是极不严格的;基础与土之间的动力相互作用将导致周围土体发生重塑软化,且基础附近的土体(近场)软化程度明显高于远场土体(自由场土体),加之土体自身的应变软化和强度降低的内在机制将共同导致土体的周期明显延长;然而,在地震作用下,桩筏基础几乎不发生软化,这与土体有着本质的区别;在相同条件下,基础的共振周期小于土体周期(近场和远场),远场土体(自由场土体)周期小于基础附近的土体周期(近场土体);土体的动力软化对结构的影响甚微

两阶段变刚度桩筏基础承载力可靠度分析及其在高层建筑基础的应用

通过建立承载力计算的极限状态方程,结合工程实例,运用可靠度理论,对两阶段变刚度桩筏基础的承载力进行了可靠度分析与验证,对其安全系数指标和可靠度指标的关系进行了研究分析,得到了基于概率极限状态设计方法即现行规范《建筑结构可靠度设计统一标准》的可靠度指标,验证了采用安全系数法作为两阶段变刚度桩筏基础承载力验(计)算方法的合理性

桩–筏–土体系的地震软化行为及ABAQUS模拟研究

通过开展离心机动力试验,充分揭示在地震荷载的持续作用下,土体将发生一定程度的软化,表现为周期的持续增大;然而基础(筏板)周期和桩身弯矩包络图几乎不发生改变,说明整个桩–筏结构在地震作用下的行为不会类似于土体发生软化(恶化的现象),而是能持续保持稳定,其动力行为主要取决于自身特性如桩身刚度和上部结构传递给筏板的荷载水平(惯性)等,同时土体的动力软化效应对桩–筏结构的影响很小。为了验证试验结果的正确性和合理性,采用ABAQUS 6.9程序对试验结果进行计算分析,土体模型包括软件内嵌的Hypoelastic非线性模型和所开发的考虑动力降强效应的HyperMas用户子程序模型(UMAT)。计算结果符合试验实测结果,尤其能准确地捕捉桩身最大弯矩值和周期等重要的工程设计参数。且有侧重于基础单元的地震响应分析,非降强模型和降强模型的计算差异很小,再次说明土体软化对既有桩–筏结构影响很小,但采用非降强模型计算更为快捷、高效