【作者】 王建峰；

【导师】 王元战； 秦延龙；

【作者基本信息】 天津大学 ， 港口海岸及近海工程， 2012， 博士

【摘要】 桶形基础作为一种新型的海洋平台基础,在近海边际油田开发中有着广阔的应用前景。近海浅滩地区软黏土中桶形基础在竖直荷载、水平荷载和弯矩荷载共同作用下的承载力特性直接关系到桶形基础在工程上的应用和推广。本文针对近海浅滩地区软黏土中桶形基础的复合承载力特性进行研究,主要研究工作有以下几个方面:首先建立桶形基础有限元模型,对桶形基础的地基竖向承载性能进行了研究,通过有限元模型计算分析桶形基础地基的竖向破坏模式,阐明了汉森与魏西克地基承载力关系式能够较好地反映单桶基础和四桶基础的地基竖向承载力特性。采用Engel假设,按照三维空间问题由极限平衡法推导了单桶基础三维偏心水平承载力的计算公式;根据竖向荷载作用下单桶基础的偏心水平承载力有限元计算结果,引用竖向荷载影响系数,提出了单桶基础复合承载力的计算方法;建立四桶基平台有限元模型,由四桶基平台竖向荷载作用下偏心水平承载力分析计算结果,建立四桶基平台复合承载力与单桶基础复合承载力的关系,确定四桶基平台复合承载力的计算方法。根据Anderson等所提出的软黏土循环强度概念,在软黏土循环三轴试验基础上,建立复合加载模式下桶形基础的三维弹塑性拟静力有限元计算模型;以1000次循环振次为例,分析了单桶基础偏心水平循环承载力特性,并考虑竖向承载力对单桶基础偏心水平循环承载力的影响,建立了复合循环荷载作用下单桶基础地基承载力计算方法;建立四桶基平台的复合循环承载力有限元模型,通过计算,建立了四桶基平台复合循环承载性能与单桶基础复合承载性能的关系,从而确定四桶基平台复合循环承载性能的计算方法。开展了室内四桶基平台复合循环承载力模型试验,在室内的软黏土模型试验土池进行了不同竖向静荷载与偏心水平循环荷载共同作用下软土中四桶基平台复合承载力的模型试验,对四桶基平台的复合承载力特性进行了研究;依据模型试验结果对四桶基平台数值模拟和理论分析结果进行对比验证,证明四桶基平台计算方法的可行性。利用本文提出的计算方法,对滩海某区块可移动式桶基试采油目标平台的桶形基础承载力性能进行计算,平台基础能够满足使用荷载要求。更多还原

【Abstract】 Bucket foundation is a new technology of ocean platform,which has the broad application prospect in the offshore marginal oilfield development. The capability of horizontal, vertical and under bending moment of the bucket foundation which sitting on offshore shoal area soft clay deeply influence the application and promotion of the project. This paper conducts research on the capacity of bucket foundation, which is applied in soft clay. The main research work has the following several aspects:According to finite element model calculations, analysising the failure mode of foundation subjected to vertical load, it is clarified that Hansen and Vesic Foundation bearing capacity relationship can describe the vertical bearing capacity characteristics of single bucket and four fuckets foundation clearly.Using Engel assumption, in accordance with Three-dimensional space problems, the Formula of horizontal eccentric bearing capacity is established by the limit equilibrium method. Base on the Finite Element Analysis results of horizontal eccentric bearing capacity calculation and introducing vertical load influence coefficient, established the complex bearing capacity calculation method. Base on the Finite Element Model and results of horizontal eccentric bearing capacity calculation, established the relationship of complex bearing capacity between single bucket and four buckets. Four buckets platform complex bearing capacity calculation method was firstly proposed.Based on cyclic triaxial testing and the concept of soft clay cyclic strength which was proposed by Anderson, quasi-static three-dimensional elastic-plastic finite element model subjected to complex load was established. Take 1000 cycle for example, showed the horizontal eccentric circulating bearing capacity characteristics of bucket foundation. Considering the impact of the vertical bearing capacity to the horizontal eccentric circulating bearing capacity, proposed complex circulating bearing capacity calculation method. Base on the finite element model and results of complex circulating bearing capacity calculation, established the relationship of complex circulating bearing capacity between single bucket and four buckets. Four buckets platform complex circulating bearing capacity calculation method was firstly proposed.Conducted indoor four-bucket foundation platform model test and validated the results of finite element anlysis and formula calculations, Model tests of four-bucke foundation in the stratum are conducted to research its bearing capacity under different vertical static and horizontal eccentric cyclic loads.According to model test condition, the simulation calculations are performed by using the cyclic strength relationship of the stratum and FEM. Calculating results are in agreement with test results, which show that the horizontal eccentric cyclic bearing capacity of the bucket foundation in the soft clay can be evaluated by using FEM based on the cyclic strength relationship and calculation method in the article.By the method proposed, calculated the bearing capacity of a bucket foundation platform which is planned to use in offshore shallow water, the results showed that the bearing capacities of foundation meet the requirements更多还原