近海大直径单桩水平受荷离心模型试验和三维数值分析

发布时间：2018-06-18 16:09

本文选题：大直径 + 桩　；参考：《浙江大学》2013年硕士论文

【摘要】：近年来,随着近海工程的发展,特别是近海风电产业的迅速崛起,桩基础呈现出直径不断增大的发展趋势。国内外常见的近海风电机组桩基型式包括超大直径单桩基础、三脚架基础、导管架基础和群桩基础等。其中超大直径单桩基础(monopile)直径可达3-8m,即使其它风机群(多)桩基础的基桩直径也达1.5-2.5m。目前,p-y曲线法被公认为桩基水平非线性变形的最有效分析方法,并被美国石油协会(API)所采用。我国现行《港口工程桩基规范》(JTJ254-98)虽建议了桩基p-y曲线分析法,但基本上是对API规范的沿用。然而现有桩基p-y曲线均基于有限尺寸桩基的试验结果,对于大直径桩基难以适用。因此开展大直径桩水平受荷特性的研究具有重要的理论意义和实际指导意义。本文通过离心模型试验研究了砂性土中大直径单桩分别在水平静力和循环荷载作用下的受力和变形特性。验证了通过实测桩身弯矩推算桩身变形和桩周土反力的有效性,分别获得了干砂和饱和砂的大直径单桩水平静力p-y曲线。在修正p-y曲线初始刚度的基础上,提出了用双曲线型p-y曲线来分析水平受荷大直径单桩的内力和变形。通过开展循环加载试验,揭示了水平单向循环荷载下大直径单桩的桩身变形及内力变化特性,试验结果显示桩身变形、最大弯矩及卸载刚度近似与循环次数的对数线性相关。最后,由各循环次数下的桩身弯矩获得了大直径单桩水平循环p-y曲线,提出了循环应力比相关的p-y曲线循环弱化因子,以及相应的桩基变形累积和内力变化分析方法。进一步,基于室内三轴固结排水剪切试验等获得剪胀性砂土的物理力学特性参数,利用大型通用有限元软件ABAQUS,开展了近海大直径单桩基础在水平荷载作用下的三维有限元数值分析,揭示了加载过程中桩周土的应力路径,探讨了桩周土内摩擦角、剪胀角及桩土接触面特性等对三维数值分析模型计算结果的影响,并得到了离心模型试验的验证,进而提出了砂土海床中大直径单桩基础的合理数值分析模型及参数取值方法。最后,利用该数值分析模型分析了现有桩基承载力和变形分析方法对超大直径单桩的有效性,并提出了该型式桩基临界埋深的确定方法。
[Abstract]:In recent years, with the development of offshore engineering, especially the rapid rise of offshore wind power industry, pile foundation presents a trend of increasing diameter. The common types of offshore wind turbine pile foundation at home and abroad include super-large diameter single pile foundation, tripod foundation, jacket foundation and pile group foundation. The diameter of single pile foundation with super-large diameter can reach 3-8 m, and the diameter of foundation pile of other fan group (multi-pile foundation) is 1.5-2.5 m. At present the p-y curve method is recognized as the most effective analytical method for the horizontal nonlinear deformation of pile foundation and used by the American Petroleum Association (API). JTJ254-98) although the p-y curve analysis method of pile foundation is suggested, the API specification is adopted basically. However, the existing p-y curves of pile foundation are based on the test results of finite size pile foundation, so it is difficult to apply to large diameter pile foundation. Therefore, it is of great theoretical and practical significance to study the horizontal loading characteristics of large diameter piles. In this paper, the stress and deformation characteristics of large diameter single pile in sandy soil under horizontal static load and cyclic load are studied by centrifugal model test. The validity of calculating the deformation of pile body and the reaction force of soil around pile is verified by the measured bending moment of pile body. The horizontal static p-y curves of large diameter single pile with dry sand and saturated sand are obtained respectively. On the basis of modifying the initial stiffness of p-y curve, a hyperbolic p-y curve is proposed to analyze the internal force and deformation of a single pile with large diameter under horizontal loading. By carrying out cyclic loading tests, the deformation and internal force of large diameter single pile under horizontal unidirectional cyclic loading are revealed. The experimental results show that the deformation, maximum bending moment and unloading stiffness of pile are approximately related to the logarithmic logarithm of cycle number. Finally, the horizontal cyclic p-y curve of large diameter single pile is obtained from the bending moment of pile body under various cycles, and the cyclic weakening factor of the p-y curve is proposed, and the corresponding analytical method of pile foundation deformation accumulation and internal force change is presented. Furthermore, the physical and mechanical properties of the dilatant sand are obtained based on the laboratory triaxial consolidation and drainage shear tests. The 3-D finite element numerical analysis of offshore large diameter single pile foundation under horizontal load is carried out by using Abaqus, the stress path of soil around pile during loading is revealed, and the internal friction angle of soil around pile is discussed. The influence of shear expansion angle and pile-soil interface characteristics on the calculation results of 3D numerical analysis model has been obtained. The centrifugal model test has been verified, and a reasonable numerical analysis model and parameter selection method for single pile foundation with large diameter in sand seabed have been put forward. Finally, the validity of existing pile foundation bearing capacity and deformation analysis methods for super-large diameter single pile is analyzed by using the numerical analysis model, and a method for determining the critical buried depth of this type of pile foundation is put forward.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1

【参考文献】