共查询到20条相似文献，搜索用时 31 毫秒
1.
The stability of submarine pipelines has been extensively studied by coastal engineers in recent years. Seismic-induced pore pressure and effective stresses in the saturated porous seabed and pipeline are the main important factors in the analysis of foundation stability around submarine pipelines. The majority research of the seismic-induced dynamic response around an offshore pipeline has been limited to two-dimension cases. In this paper, a three-dimensional finite element model including buried pipeline is established by extending DYNE3WAC. Based on the proposed numerical model, a parametric study is conducted to examine the effects of soil characteristics and pipeline configurations on the seismic-induced soil response around offshore pipelines. 相似文献
2.
海上平台桶基沉贯渗流场的有限元法数值模拟 总被引：3，自引：1，他引：2
桶形基础平台是一种新型的海洋平台,这种型式的平台与传统的导管架式平台的主要区别在于采用桶形基础代替打下桩基础,桶形基础的负压沉贯过程是一个复杂的水动力过程,其关键在于主动脉施加的桶内外压力差产生渗流场,渗流场的形成与发展对于负压沉贯有决定性的影响。本文用有限元分析方法对桶形基础负压沉贯流流场进行动态模拟,建立了桶形基础负压沉贯过程中渗流场的有限元分析模型,模型试验的结果与按有限元分析计算模型得一的 相似文献
3.
Calculation of Hydro-Dynamic Stability of the Soil Inside Bucket in the Process of Bucket Foundation Penetration 总被引：1，自引：0，他引：1
—The offshore platform with bucket foundations is a new type of offshore platform that distin-guishes from traditional template platforms by replacing driven piles with bucket foundations.The suctionpenentration of bucket foundation is a complicated hydro-dynamic process.The key of this process is theseepage field caused by the difference of pressure applied on purpose inside and outside the bucket.The ap-pearance and developement of seepage field has a decisive influence on the suction penetration process.Inthis study,the finite element analysis method is applied to the dynamic simulation of the seepage field ofsuction penetration of bucket foundation.A criterion is suggested to distinguish the hydro-dynamic stabili-ty of the soil inside the bucket according to the critical hydraulic gradient method.The reliability of themodel and its applicability to engineering practice have been proved through comparison between the re-sults of model test and finite element calculation. 相似文献
4.
单立柱桶基平台整体结构静,动力分析 总被引：1，自引：0，他引：1
桶基平台是以桶形基础代替传统的桩基础,是海洋工程结构的一种新型基础形式,该平台是板壳和梁组成的空间结构,受力复杂,本文采用弹性抗力法解决桶形基础与土壤相互作用,用水平弹簧模拟桶基与土壤相互作用,采用板壳和梁的计算模型对平台结构进行分析,为平台的结构设计提供了依据。 相似文献
5.
C. J. Garrison 《Applied Ocean Research》1989,11(4):194-201
It is common practice to compute wave-induced loads on the immersed surface of gravity structures exposed to the wave motion and disregard the pore-water pressure variation on the foundation surface. However, when the soil is porous, wave-induced pressures propagate within the soil under the structure and result in a rather significant contribution to overall loads. This paper describes a practical method for numerical modeling of the pore pressure under a gravity platform foundation for compressible water and a rigid, but porous soil. The porous soil may be bounded by an impermeable horizontal layer at some arbitrary depth.
The paper outlines the basic boundary element procedure for pore pressure analysis and presents numerical results for a typical gravity structure as well as results for comparison with an existing analytical solution for a vertical circular cylinder. 相似文献
6.
将衬砌分别视为多孔柔性材料和弹性介质,在频率域内研究内水压力作用下饱和分数导数黏弹性土-深埋圆形隧洞多孔柔性或弹性衬砌系统的耦合简谐振动。土体的宏观力学特性采用多孔介质理论来模拟。通过引入与土体体积分数相关的应力系数,利用衬砌和土体界面处位移连续,分别得到饱和黏弹性土和衬砌的位移、应力和孔隙水压力等的解析表达式。在此基础上,分析了多孔柔性衬砌和弹性衬砌结构的差异,并考察了应力系数、渗透系数、分数阶导数本构参数等对系统动力响应的影响,结果表明:多孔柔性衬砌材料条件下系统的动力响应明显大于弹性衬砌材料条件下系统的动力响应;随着分数导数阶数和材料参数比的增加,系统共振效应明显减弱;衬砌边界透水和不透水只是反映边界渗透性的两种极限状态。 相似文献
7.
-Dynamic interaction characteristics of the model deeply embedded platform and foundation soil are studied by means of dynamic substructuring interface transformation synthesis and dynamic condensation. The theoretical analysis, computer programs and practical examples are presented; and the results are compared with those obtained by statical condensation method and finite element method. 相似文献
8.
Zhong Wanxie Yao Shizhong Wu Lianyuan Xi Deyin Professor Shanghai Jiao Tong University Shanghai Engineer Shanghai Jiao Tong University Shanghai Lecturer Shanghai Jiao Tong University. Shanghai 《中国海洋工程》1993,(4)
- In this paper, the authors use the finite element method to conduct a special static analysis for the loadout procedure of offshore structures. By introducing a variable Xmove (the distance between the relative coordinate system fixed in the moving upper structure and the absolute coordinate system fixed on slideway), adopting substructure to treat the upper structure, and using the elastic foundation beam to model the slideway, the model for the analysis of the loadoul procedure is established. On the basis of this model, DASOS-J loadout program, a program system for the static analysis of loadout offshore structures, is also developed. 相似文献
9.
以某122 m自升式钻井平台为分析对象,建立其有限元模型,包括材料非线性、几何非线性以及桩土非线性相互作用,在风浪流作用下,基于三维约束New Wave理论对自升式钻井平台的动态响应进行分析,研究海洋波浪方向传播特性和随机特性对平台动力响应的影响。在建立模型中实现风暴工况下水面高程和水粒子运动的描述,响应结果按甲板位移进行对比。结果表明,相比其它波浪理论,三维约束New Wave理论在平台动力响应分析中体现了一定的优越性,不仅能较准确地反映波浪的真实特性,而且能确保结构性能评估的安全性和合理性。 相似文献
10.
11.
导管架平台桩基贯入深度的两级模糊模式优选模型 总被引：1，自引：0，他引：1
桩基础是海洋导管架平台结构中的重要组成部分，其贯入深度对海洋平台的造价和运营期间的安全性能起着重要的影响。本文在考虑桩－土之间相互作用非线性特性的基础上，采用非线性等效弹筑模拟海底土层对桩基的作用，对桩基进行有限元分析。由于影响海洋导管架平台桩基础贯入深度的因素很多，而且有些因素带有很大的模糊性，本文采用两级模糊模式优选模型对影响因素进行综合评判，最后得出了适合给定荷载和海底地条件下最为合理的桩基贯入深度方案，具有一定的工程应用价值。 相似文献
12.
正压冲固平台是一种采用短桩加固基础的新型海洋采油平台，对于这种新型的平台结构，在结构分析和构件强度校核中必须考虑其有限元模型的基础边界条件处理问题。本文提出了正压冲固平台有限元计算模型中基础边界条件的一种简化方法，将两个水平方向的扭转自由度简化为扭转弹簧边界元，其余自由度简化为固定约束。通过计算分析得到了不同的边界约束刚度系数的取值对平台总体位移和强度校核应力的影响及变化趋势。结论是，平台结构对约束刚度系数K的反应在10^4～10^4之间时比较明显，对K的敏感度最为强烈：在此范围之外，平台反应分别接近于简支约束情况和刚性约束情况。尤其对于接近约束边界的单元，其应力变化最敏感。 相似文献
13.
筒型基础有限元分析的土体边界选取研究 总被引：4，自引：0，他引：4
利用通用的有限元程序ANSYS软件,以歧口17—2筒型基础平台为对象,采用三维八结点的块体等参元,在相同荷载和约束条件下,选取不同的土体边界,就筒型基础筒边土体的附加应力扩散行为进行了三维有限元分析。分析结果表明,筒边土体的附加应力扩散规律具有方向性;在确定土体边界尺寸时,应在水平方向取土体边界尺寸为5．0倍简体直径,在竖直方向取土体边界尺寸为2．0倍筒高,此时就可以忽略土体的边界效应,进而在有限元计算精度和求解时间之间找到一个合理的平衡点。 相似文献
14.
自升式钻井平台插桩是地基土在桩靴荷载作用下发生连续的塑性破坏的动态过程,当地基极限承载力等于桩靴荷载时插桩完成。经典土力学极限承载力理论对土体潜在滑动面做了假设,无法有效分析土体内部的破坏过程。本研究应用有限元法（FEM ）对插桩过程进行了模拟,得到地基土的破坏机制以及中间荷载下土体的应力、应变情况,通过和各理论公式计算的极限承载力进行对比分析,分析影响地基极限承载力的因素。研究表明,基础宽度与硬土层厚度的比值 B/H越大,下卧软土层越容易发生塑性破坏,极限承载力明显下降,当B/H＜0．286时,可以忽略下卧软土层对地基承载力的影响。 相似文献
15.
基于广义Biot动力理论和Longuet-Higgins线性叠加模型,构建波浪-海床-管线动态响应的有限元计算模型,求解随机波作用下,多层砂质海床中管线周围土体孔隙水压力和竖向有效应力的分布。采用基于超静孔隙水压力的液化判断准则,得出液化区的最大深度及横向范围,从而判断海床土体液化情况。考虑海洋波浪的随机性,将海床视为多孔介质,海床动态响应计算模型采用u-p模式,孔隙水压力和位移视为场变量。并考虑孔隙水的可压缩性、海床弹性变形、土体速度、土体加速度以及流体速度的影响,忽略孔隙流体惯性作用。参数研究表明:土体渗透系数、饱和度以及有效波高等参数对海床土体孔隙水压力、竖向有效应力和液化区域分布有显著影响。 相似文献
16.
采用弹性基础梁模型,模拟钢悬链线立管(steel catenary riser,SCR)与海床土的相互作用,推导了弹性基础梁模型的有限元公式,基于该模型编制了钢悬链式立管的动力分析程序,在此基础上,分析了在浮体运动及环境载荷作用下,钢悬链线立管触地点区域的动力响应特征,并与弹簧支撑模型进行了比较。研究表明,弹性基础梁模型对单元长度的敏感性较低,可采用较长的单元,从而减少计算量。 相似文献
17.
海工结构物浅基础稳定性的可靠度分析 总被引：5，自引：1，他引：5
应用可靠度理论对渤海某油田软粘土地基工作的沉垫式基础的稳定性进行了可靠度分析，阐述了各个设计指标的变化对分项系数及可靠度指标的影响规律，并将分析结果与该标准中规定的分项系数进行了比较。 相似文献
18.
He Guangna Cao Yalin
Professor Dalian University of Technology Dalian .
Former Postgruate Student Dalian University of Technology Dalian 《中国海洋工程》1995,(2)
Based on unified equivalent harmonic loading on seabed foundation and energy approach suggested by the authors, the development of dynamic pore water pressure and stability of soil foundation for the vibration of ocean gravity structures excited by random wave loading are analysed. It may be seen that the present method for the study of dynamic problems of ocean gravity structure soil foundations is more reasonable and convenient. 相似文献
19.
Study of the Bearing Capacity at the Variable Cross-Section of A Riser-Surface Casing Composite Pile
Reducing the cost of offshore platform construction is an urgent issue for marginal oilfield development.The offshore oil well structure includes a riser and a surface casing.The riser,surface casing and oil well cement can be considered special variable cross-section piles.Replacing or partially replacing the steel pipe pile foundation with a variable cross-section pile to provide the required bearing capacity for an offshore oil platform can reduce the cost of foundation construction and improve the economic efficiency of production.In this paper,the finite element analysis method is used to investigate the variable cross-section bearing mode of composite piles composed of a riser and a surface casing in saturated clay under a vertical load.The calculation formula of the bearing capacity at the variable section is derived based on the theory of spherical cavity expansion,the influencing factors of the bearing capacity coefficient Nc are revealed,and the calculation method of Nc is proposed.By comparing the calculation results with the results of the centrifuge test,the accuracy and applicability of the calculation method are verified.The results show that the riser composite pile has a rigid core in the soil under the variable cross-section,which increases the bearing capacity at the variable cross-section. 相似文献
20.
桶型基础是一种新型的海洋基础结构型式，在负压作用下的下沉过程中，桶型基础结构与地基产生了相互作用，考虑结构与土壤的相互作用的强度分析为桶型基础的设计提供依据，本文将有限元－无限地－接触元相耦合的线性数值分析方法引入桶型基础的结构与土壤之间的相互作用的强度分析，采用接触单元考虑结构与土壤之间的错动滑移及拉裂，采用无限元更有效地反映地基无限域的远场效应，还推导出三节点，七节点，八节点三种新形式的单向无限地坐标映射函数，应用该方法的计算结果与模型试验结果比较，取得较好的效果。 相似文献