非均质粘土中海洋桩靴基础的失效机理研究
发布时间：2018-11-19 18:20
【摘要】：海洋桩靴基础是自升式海上石油和天然气开发平台的重要组成部分。这种自升式海上开发平台一般安装在浅海至中等水深的海域。海洋桩靴基础通常为倒圆锥形,桩靴基础通常埋入海床土体中深至三倍基础直径的深度,以获得足够的承载力。虽然有学者对桩靴基础在均质土和多层土体中的失效机理和承载力进行了研究,但土体的空间变异性对桩靴基础在非均质粘土中承载力的影响目前还不清楚。本文通过将随机有限元方法和蒙特卡洛模拟理论结合,发展了考虑粘土空间变异性时桩靴基础(Spudcan)失效机理和承载力的研究方法。海床土体特性在空间水平、竖直方向都会变化,本研究中空间变异性是指海床土体的不排水剪切强度的变异性。本文首先阐述了海床土体的随机特性,通过随机场理论模拟海床土体的空间变异性,并结合有限元理论研究了海洋桩靴基础的承载力及失效机理。桩靴基础形状按真实的基础形状简化后模拟,将模拟结果与已有文献进行对比,验证了本研究方法的正确性。结果表明,桩靴基础在非均质土上的承载力取决于剪切经过的路径大小以及剪切面经过的土体不排水剪切强度的高低。随机有限元方法结合蒙特卡洛模拟的方法分析土体水平和竖直方向空间变异性对海洋桩靴基础承载力和失效机理的影响。本文进一步研究了土体的各向同性和各向异性对桩靴基础的影响,研究结果显示随着土体各向异性的增大,桩靴基础在非均质土上的承载力均值逐渐变小。当非均质土的水平空间相关长度为基础的宽度的三倍时,桩靴基础的承载力变异系数随空间变异性的增加而减小。当非均质土的竖向相关长度为3 m时,桩靴基础的承载力变异系数随空间变异性的增大而增加。研究了桩靴基础在非均质土上的安全系数和失效概率。结果表明当非均质土的水平空间相关长度为基础的宽度的三倍时,随空间变异性的增加,靴基础的失效概率逐渐增大,但对应某一失效概率时的安全系数逐渐变小。当非均质土的竖向相关长度为3 m时,随空间变异性的增加,桩靴基础的失效概率逐渐变小,但对应某一失效概率时的安全系数逐渐变大。
[Abstract]:Offshore pile-boots foundation is an important part of self-elevating offshore oil and gas development platform. This self-elevating offshore development platform is generally installed in shallow to medium-depth waters. The pile shoe foundation is usually inverted conical, and the pile shoe foundation is usually buried in the seabed soil to the depth of three times the diameter of the foundation in order to obtain sufficient bearing capacity. Although some scholars have studied the failure mechanism and bearing capacity of pile boot foundation in homogeneous soil and multi-layer soil, the effect of soil spatial variability on the bearing capacity of pile boot foundation in heterogeneous clay is not clear. In this paper, by combining stochastic finite element method with Monte Carlo simulation theory, the (Spudcan) failure mechanism and bearing capacity of pile-boot foundation considering the spatial variability of clay are developed. In this study, the spatial variability refers to the variability of the undrained shear strength of the seabed soil. In this paper, the random characteristics of the seabed soil are described, the spatial variability of the seabed soil is simulated by the random field theory, and the bearing capacity and failure mechanism of the pile boot foundation are studied with the finite element theory. The shape of pile and boot foundation is simplified according to the real foundation shape and the simulation results are compared with the existing literatures to verify the correctness of this method. The results show that the bearing capacity of pile boot foundation on heterogeneous soil depends on the size of the shear path and the undrained shear strength of the soil passing through the shear plane. The influence of horizontal and vertical spatial variability of soil on the bearing capacity and failure mechanism of offshore pile boot foundation is analyzed by means of stochastic finite element method and Monte Carlo simulation. The influence of isotropy and anisotropy of soil on the pile-boot foundation is further studied in this paper. The results show that with the increase of soil anisotropy, the average bearing capacity of the pile-boot foundation decreases gradually in heterogeneous soil. When the horizontal spatial correlation length of the heterogeneous soil is three times the width of the foundation, the coefficient of variation of the bearing capacity of the pile-boot foundation decreases with the increase of the spatial variability. When the vertical correlation length of heterogeneous soil is 3 m, the coefficient of variation of bearing capacity of pile and boot foundation increases with the increase of spatial variability. The safety factor and failure probability of pile-boot foundation in heterogeneous soil are studied. The results show that when the horizontal spatial correlation length of the heterogeneous soil is three times of the base width, the failure probability of the boot foundation increases with the increase of spatial variability, but the safety factor of the boot foundation becomes smaller with the corresponding failure probability. When the vertical correlation length of heterogeneous soil is 3 m, the failure probability of pile-boot foundation becomes smaller with the increase of spatial variability, but the safety factor of the pile and boot foundation increases gradually with a certain failure probability.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU476;P75
本文编号：2343055
[Abstract]:Offshore pile-boots foundation is an important part of self-elevating offshore oil and gas development platform. This self-elevating offshore development platform is generally installed in shallow to medium-depth waters. The pile shoe foundation is usually inverted conical, and the pile shoe foundation is usually buried in the seabed soil to the depth of three times the diameter of the foundation in order to obtain sufficient bearing capacity. Although some scholars have studied the failure mechanism and bearing capacity of pile boot foundation in homogeneous soil and multi-layer soil, the effect of soil spatial variability on the bearing capacity of pile boot foundation in heterogeneous clay is not clear. In this paper, by combining stochastic finite element method with Monte Carlo simulation theory, the (Spudcan) failure mechanism and bearing capacity of pile-boot foundation considering the spatial variability of clay are developed. In this study, the spatial variability refers to the variability of the undrained shear strength of the seabed soil. In this paper, the random characteristics of the seabed soil are described, the spatial variability of the seabed soil is simulated by the random field theory, and the bearing capacity and failure mechanism of the pile boot foundation are studied with the finite element theory. The shape of pile and boot foundation is simplified according to the real foundation shape and the simulation results are compared with the existing literatures to verify the correctness of this method. The results show that the bearing capacity of pile boot foundation on heterogeneous soil depends on the size of the shear path and the undrained shear strength of the soil passing through the shear plane. The influence of horizontal and vertical spatial variability of soil on the bearing capacity and failure mechanism of offshore pile boot foundation is analyzed by means of stochastic finite element method and Monte Carlo simulation. The influence of isotropy and anisotropy of soil on the pile-boot foundation is further studied in this paper. The results show that with the increase of soil anisotropy, the average bearing capacity of the pile-boot foundation decreases gradually in heterogeneous soil. When the horizontal spatial correlation length of the heterogeneous soil is three times the width of the foundation, the coefficient of variation of the bearing capacity of the pile-boot foundation decreases with the increase of the spatial variability. When the vertical correlation length of heterogeneous soil is 3 m, the coefficient of variation of bearing capacity of pile and boot foundation increases with the increase of spatial variability. The safety factor and failure probability of pile-boot foundation in heterogeneous soil are studied. The results show that when the horizontal spatial correlation length of the heterogeneous soil is three times of the base width, the failure probability of the boot foundation increases with the increase of spatial variability, but the safety factor of the boot foundation becomes smaller with the corresponding failure probability. When the vertical correlation length of heterogeneous soil is 3 m, the failure probability of pile-boot foundation becomes smaller with the increase of spatial variability, but the safety factor of the pile and boot foundation increases gradually with a certain failure probability.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU476;P75
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