【作者】 陈宁；

【导师】 黎冰； 周进军；

【作者基本信息】 东南大学 ， 建筑与土木工程（专业学位）， 2021， 硕士

【摘要】 水平受荷桩在工程中非常普遍,如海上风电和港口码头等工程中的桩。现行的桩基础设计采用的是确定性分析方法,可靠度保障方面采用的也是统一的安全系数法,而地基土是自然界的产物,具有天然的空间变异性。因此,将土体作为一个随机场,考虑土体空间变异性对桩基础的影响是十分必要的。本文以土体不排水强度为随机变量,针对海上风机钢管桩基础建立三维模型,应用随机有限元法研究了土性空间变异性对水平受荷桩的影响。主要工作和成果如下:(1)针对三维随机场谱表示法生成的随机场单元无法与有限元单元直接对应的问题,提出了一种有效的随机场数据单元转换方法,完成了规则随机场单元向不规则有限元单元的对应过程,实现了随机场数据向有限元单元的导入。(2)以土体不排水强度为随机变量,考虑不同的相关距离,开展了水平荷载作用下单桩基础的三维模拟分析。结果发现:考虑土体空间变异性的单桩水平承载力均值皆小于确定性分析结果;随机场相关距离对承载力均值无明显影响,承载力标准差和变异系数随相关距离的增大而增大。此外,考虑土体空间变异的单桩水平承载力符合对数正态分布。(3)开展了非平稳随机场下水平受荷桩的三维模拟,并与平稳随机场的结果进行了对比分析。结果表明:随着土体随机场非平稳系数的增大,单桩水平承载力逐渐增大,变异系数逐渐减小;与平稳随机场下的单桩水平承载力相比,非平稳随机场下单桩水平承载力均值更大,变异系数要小。(4)开展了水平荷载作用下单桩基础的二维模拟,并与三维随机模拟结果进行了对比分析。结果表明:二维随机场下单桩水平承载力与三维随机场下计算的结果表现出一致的规律性,即均值不受相关距离的影响,随非平稳系数的增大而增大;承载力变异系数随相关距离的增大而增大,随非平稳系数的增大而减小。但三维随机场模拟的单桩承载力规格化均值大于二维模拟结果,变异系数小于二维计算结果,相关距离和非平稳系数的变化对三维单桩水平承载力的影响更小。更多还原

【Abstract】 Horizontally loaded piles are common in engineering,such as piles in offshore wind power and port projects.The deterministic analysis method is used in current pile foundation design,and the unified safety factor is used to guarantee the reliability of foundation.The foundation soil is a product of nature and has natural spatial variability.Therefore,it is necessary to take the soil as a random field and consider the influence of the spatial variability of the soil on the pile foundation.In this paper,the undrained strength of the soil is used as a random variable,and a three-dimensional model is established for the offshore wind turbine single-pile foundation.The stochastic finite element method(RFEM)is used to study the influence of the spatial variability of soil properties on the horizontally loaded pile.The main work and results are as follows:(1)To solve the problem that the random field units generated by the three-dimensional random field spectral representation method is a regular cuboid of the same size,and its data cannot be directly imported into irregular hexahedral finite element units of different sizes,an effective coordinate space conversion method is proposed.The coordinate space conversion method realizes the corresponding process from regular random field elements to irregular finite element elements.(2)Considering the undrained strength of the soil as a random variable and recommending different correlation distance,a three-dimensional simulation analysis of a single pile foundation under horizontal load was carried out.The results show that the mean of the horizontal bearing capacity of a single pile considering the spatial variability of the soil is less than the deterministic analysis result.The correlation distance of the random field has no significant effect on the average bearing capacity,while the standard deviation of the bearing capacity and the coefficient of variation increase with the increase of the relative distance.In addition,the horizontal bearing capacity of a single pile considering the spatial variability of the soil conforms to a lognormal distribution.(3)A three-dimensional simulation of a horizontally loaded pile under non-stationary random field was carried out,and a comparative analysis was carried out with the result of stationary random field.The results show that with the increase of the non-stationary coefficient of the soil random field,the horizontal bearing capacity of a single pile gradually increases,and the coefficient of variation gradually decreases.Compared with the horizontal bearing capacity of a single pile in stationary random field,the mean of horizontal bearing capacity of a single pile in a non-stationary random field is larger,and the coefficient of variation is smaller.(4)A two-dimensional simulation of a single pile foundation under horizontal load was carried out,and a comparative analysis was carried out with the three-dimensional random simulation results.The results show that the horizontal bearing capacity of a single pile under a two-dimensional random field is consistent with the results calculated under a threedimensional random field.The mean value is not affected by the correlation distance,and increases with the increase of the non-stationary coefficient.The coefficient of variation increases with the increase of the correlation distance,and decreases with the increase of the non-stationary coefficient.However,the normalized mean value of the single pile bearing capacity simulated by the three-dimensional random field is larger than the two-dimensional simulation results,and the coefficient of variation is smaller than the two-dimensional calculation results.The changes in the correlation distance and non-stationary coefficient have a greater impact on the horizontal bearing capacity of the two-dimensional single pile.更多还原