Impedance of flexible suction caissons     

Morten Liingaard  Lars Andersen  Lars Bo Ibsen 《地震工程与结构动力学》2007,36(14):2249-2271

The dynamic response of offshore wind turbines is affected by the properties of the foundation and the subsoil. The aim of this paper is to evaluate the dynamic soil–structure interaction of suction caissons for offshore wind turbines. The investigations include evaluation of the vertical and coupled sliding–rocking vibrations, influence of the foundation geometry and examination on the properties of the surrounding soil. The soil is simplified as a homogenous linear viscoelastic material and the dynamic stiffness of the suction caisson is expressed in terms of dimensionless frequency‐dependent coefficients corresponding to different degrees of freedom. The dynamic stiffness coefficients for the skirted foundation are evaluated using a three‐dimensional coupled boundary element/finite element model. Comparisons with known analytical and numerical solutions indicate that the static and dynamic behaviours of the foundation are predicted accurately using the applied model. The analysis has been carried out for different combinations of the skirt length, Poisson's ratio of the subsoil and the ratio of the soil stiffness to the skirt stiffness. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Modelling peak accelerations from earthquakes   总被引：1，自引：0，他引：1  

Debbie J. Dupuis  Joanna Mills Flemming 《地震工程与结构动力学》2006,35(8):969-987

This paper deals with the prediction of peak horizontal accelerations with emphasis on seismic risk and insurance concerns. Non‐linear mixed effects models are used to analyse well‐known earthquake data and the consequences of mis‐specifying assumptions on the error term are quantified. A robust fit of the usual model, using recently developed robust weighted maximum likelihood estimators, is presented. Outlying data are automatically identified and subsequently investigated. A more appropriate model accounting for the extreme value nature of the responses, is also developed and implemented. The implication on acceleration predictions is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

圆形断面管道非满流流速计算表达式   总被引：1，自引：0，他引：1       下载免费PDF全文

茅泽育  赵璇  罗昇 《水科学进展》2007,18(2):170-174

工程实际中,常需要计算某一充满度下管道非满流的流量及流速。目前大多数计算模型均采用水力半径作为反映过流断面形状及几何尺寸的特征参数。针对不同充满度的研究结果表明,这种类型模型的计算结果与真实的流动特性并不相符,尤其当水深接近管顶时。根据水动力学基本原理及试验研究手段,对圆形断面管道无压均匀流流量-充满度非单一性进行了探索,并提出了以流量作为形状特征参数的更为合理且简单实用的水流流速计算表达式。  相似文献   

A new solution for a partially penetrating constant‐rate pumping well with a finite‐thickness skin     

Pin‐Yuan Chiu  Hund‐Der Yeh  Shaw‐Yang Yang 《国际地质力学数值与分析法杂志》2007,31(15):1659-1674

A mathematical model describing the constant pumping is developed for a partially penetrating well in a heterogeneous aquifer system. The Laplace‐domain solution for the model is derived by applying the Laplace transforms with respect to time and the finite Fourier cosine transforms with respect to vertical co‐ordinates. This solution is used to produce the curves of dimensionless drawdown versus dimensionless time to investigate the influences of the patch zone and well partial penetration on the drawdown distributions. The results show that the dimensionless drawdown depends on the hydraulic properties of the patch and formation zones. The effect of a partially penetrating well on the drawdown with a negative patch zone is larger than that with a positive patch zone. For a single‐zone aquifer case, neglecting the effect of a well radius will give significant error in estimating dimensionless drawdown, especially when dimensionless distance is small. The dimensionless drawdown curves for cases with and without considering the well radius approach the Hantush equation (Advances in Hydroscience. Academic Press: New York, 1964) at large time and/or large distance away from a test well. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

明基床上开孔沉箱垂直力峰值对应的水平力分析          下载免费PDF全文

孙大鹏  张玉彬  夏志盛  吴浩 《海洋工程》2014,32(6):49-58

利用水槽二维物理模型对规则波及不规则波作用下明基床上开孔沉箱所受到的波浪力进行了较为系统的试验研究。分析了开孔沉箱总垂直力峰值时刻对应的总水平力与相对基床高度、消浪室相对宽度、波陡、相对水深以及开孔率等影响因素之间的关系,给出了明基床上开孔沉箱总水平力比值(总垂直力峰值时刻对应的总水平力/总水平力峰值)与各影响因素之间的计算关系式。研究成果可供实际工程参考应用。  相似文献   

Factor of safety in a partially saturated slope inferred from hydro‐mechanical continuum modeling     

Ronaldo I. Borja  Joshua A. White  Xiaoyu Liu  Wei Wu 《国际地质力学数值与分析法杂志》2012,36(2):236-248

Rainfall weakens an earth slope and triggers mass movement. Relevant triggering mechanisms are complex and include reduction of capillary pressure due to increased saturation and frictional drag on the sediment induced by fluid flow. Physics‐based continuum models utilizing modern computational tools are useful for understanding the mechanisms of deformation in partially saturated slopes; however, they do not provide a scalar indicator called ‘factor of safety’ that measures the potential of a given slope for mass movement. In the present work, we employ sequential calculations consisting of a physics‐based finite element model that couples solid deformation with fluid flow to quantify the stress and deformation fields in a steep hillside slope subjected to rainfall infiltration. This is followed by a limit‐equilibrium calculation based on the method of slices that evaluates the desired factor of safety. The field condition investigated is similar to the steep experimental catchment CB1 near Coos Bay, Oregon, which failed as a large debris flow from heavy rainfall. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Scattering of elastic wave by a partially sealed cylindrical shell embedded in poroelastic medium     

Liu Gan‐Bin  Xie Kang‐He  Yao Hai‐lin 《国际地质力学数值与分析法杂志》2005,29(11):1109-1126

Scattering of an elastic wave by a cylindrical shell embedded in poroelastic medium is investigated theoretically with the assumption that the shell material is also a porous elastic medium. The porous medium is modellized via Biot's theory and the scattering by cylindrical shell is expressed by the definition of scattering matrix. The normal mode expansion technique is employed for analysing the scattering field, and the asymptotic solutions of displacements, stresses and pore pressure are derived. Two limiting cases‐scattering by a poroelastic cylinder in Biot medium and a elastic cylindrical shell in elastic medium are obtained from the general solutions. The dispersion curves of displacement amplitude at the interface of shell and medium is compared with the case of elastic shell. The scattering amplitude associated with the fast, slow and transverse waves are identified by numerical simulation. Furthermore, the influence of the poroelastic property of shell material on scattering amplitude is analysed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

分层土中裙式吸力基础吸力沉贯特性模型试验研究     

张雨坤  秦廷辉  李大勇  王冲冲 《岩土力学》2022,43(5):1317-1325

针对一种新型海上风电基础形式-裙式吸力基础,开展模型试验,研究其在分层土地基中的沉贯特性。讨论了土层分布形式（砂土、黏性土、上层砂土及下层黏性土（简称上砂下黏）、上层黏性土及下层砂土（简称上黏下砂））、沉贯方式的影响。研究表明：裙式吸力基础在分层土中具有良好的沉贯性能。与传统吸力基础相比,裙式吸力基础在砂土、黏性土、上砂下黏和上黏下砂地基中最终沉贯深度较传统吸力基础分别增加10.0%、2.3%、3.0%和9.6%,沉贯最大吸力值分别增加0.9%、14.4%、66.2%和92.2%。黏性土层位置和厚度对基础沉贯特性影响显著。上黏下砂地层中,基础最大吸力值出现在土层分界面处,最大吸力值随土层分布系数t（上层土厚度与土体总厚度的比值）的增加而逐渐增大,最终沉贯深度随土层分布系数增加而逐渐减小。上砂下黏地层中,裙式吸力基础最大吸力值出现在最大沉贯深度处,吸力最大值随土层分布系数的增加而逐渐减小,最终沉贯深度受土层分布系数影响较小。此外,同时抽吸主桶和裙结构内水体进行沉贯,最终沉贯深度大于只抽主桶情况。在砂土、黏性土、上黏下砂（ 0.4）和上砂下黏（ 0.4）等4种地基中,裙式吸力基础采用同时抽主桶和裙结构的沉贯方式,最终沉贯深度较只抽主桶情况分别增大了13.8%、3.4%、16.4%和4.6%。研究成果为进一步阐明吸力基础在分层土中沉贯机制及指导工程实践,具有借鉴意义。  相似文献   

超大沉井基础取土下沉刃脚土压力变化规律研究     

蒋凡  刘华  岳青  杨文爽 《岩土力学》2022,43(Z2):431-442

依托常泰长江大桥主塔沉井基础工程,采用三维有限元方法,模拟了大型沉井首次取土下沉阶段刃脚土压力的变化过程,并结合现场刃脚土压力实测数据,分析了沉井下沉工序对刃脚土压力分布的影响以及取土过程中刃脚土压力的变化规律。现场监测结果表明：刃脚实际土压力变化规律基本上佐证了数值模拟结果。井孔内取土导致取土区域沉井刃脚处土压力下降,取土区域刃脚土压力随取土厚度的增大而逐渐降低,土体压应力转移至尚未取土区域的刃脚处。在由内井孔向外井孔区域取土的过程中,刃脚土压力向外井孔刃脚区域转移,导致外井壁和外隔墙区域刃脚土压力逐渐增大,直至达到其极限承载力,外井壁区域土体进入塑性状态,沉井出现明显下沉。给出的沉井刃脚处土压力的变化规律可为同类大型沉井可控下沉提供指导。  相似文献   

Mixing caused by lateral internal seiching within a partially mixed estuary     

K.R. Dyer 《Estuarine, Coastal and Shelf Science》1982,15(4):443-457

The salinity fluctuations at an STD near the halocline in Southampton Water have been spectrally analysed. Mixing is shown to commence at a layer Richardson number of about 20. The predominant energy inputs have periods of 7–9 and 3·5–4·5 min. These motions arise from lateral internal seiching and it is considered that they are produced by interaction of the surface seiche with the shallow side of the estuary. The wavelengths of the standing wave are calculated to be about 120 and 60 m respectively, and these compare well with echo-sounding surveys of the elevation of the halocline.  相似文献