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海上风电场桩基局部冲刷是工程设计与运行阶段的重要参数之一。基于湛江某海上风电场桩基3次现场局部冲刷实测数据,进行冲刷坑最大深度、冲刷坑半径和冲淤变化特征的分析与研究;根据桩基局部冲刷经验公式,采用工程海域实测海洋水文动力学数据进行最大冲刷深度与冲刷半径的计算,并进行公式计算值的对比与分
析。结果表明:桩基础在防冲刷设施的保护下,3次实测最大冲刷深度基本稳定为4.0 m,最大冲刷深度与桩径之比为0.57。而经验公式的最大冲刷深度与桩径之比均超过了1.1,说明桩基防冲刷设施取得了一定的效果,冲刷坑半径的计算值与现场实测值吻合较好。建议海上风电场在运行阶段进一步加强桩基冲刷坑监测与防护。 相似文献
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为减轻海上风电单桩基础周围局部冲刷对其结构安全的影响,提出了一种新型旋转减冲装置。在波流水槽中开展物理模型试验,改变波流条件、装置安装高度、安装距离,记录桩周冲刷发展历时,运用激光地形仪扫描冲刷坑形态,分析各工况下冲刷坑形态差异,验证装置不同安装距离、安装高度下的冲刷防护效果,提出了不同安装位置下的防护效率公式。结果表明：新型旋转减冲装置具有较好的冲刷防护效果,本试验工况下,桩周最大冲刷深度可减小44%左右。装置安装距离对冲刷防护效果影响较小,波流作用下的冲刷防护效果受装置安装高度影响显著,冲刷防护效果随装置安装高度的增加而减弱。 相似文献
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根据2018年多波束测深系统、双频ADCP获得的横沙岛北侧岸坡水下地形与水动力实测数据,并结合历史地形资料分析该区域冲刷特征与发展趋势。结果表明:横沙北侧岸坡存在近岸冲刷坑,最大冲深约7 m;2002—2018年期间,冲刷坑附近河床经历冲-淤-冲的演变模式,整体呈冲刷状态;2007年后冲刷坑开始形成,并向下游延伸。这主要是因为青草沙水库工程的建设导致北港上段束窄,下段主流南移贴岸,使得近岸河床冲刷加剧。另外,横沙东滩促淤圈围工程抑制了北港与北槽间的水量交换,横沙岛近岸水域水动力进一步增强,也是岸坡冲刷的原因之一。分析表明大潮期间水流处于次饱和状态,岸坡表层泥沙起动流速略小于落急时刻水流流速,横沙北侧岸坡的冲刷可能会继续发展。 相似文献
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综合国内外现有研究成果，分析了桩周流场结构及局部冲刷坑的分布形态，通过三维数值模拟，验证了局部冲刷最大值点出现在桩前，且冲坑坡度近似等于泥沙水下休止角的结论。从国内外规范内局部冲深计算公式中筛选出跨海桥梁钢管桩局部冲刷深度的主要影响因素。基于能量平衡理论，通过来流水流搬运冲刷坑内泥沙过程中的能量守恒，推导了概念清晰、形式简单的局部冲刷深度预测公式。区别于现有多数公式主体结构，该公式为关于局部冲深的一元三次方程，通过水下泥沙休止角来考虑泥沙对冲刷的影响以及冲刷过程中冲刷坑自身深度及范围变化对冲刷产生的影响。利用最小二乘法，结合环杭州湾区域三座跨海大桥的试验及实测数据拟合确定了公式相关参数，并与国内外规范内的公式对比验证，结果表明，该公式精度较高，可为实际工程计算分析提供参考。 相似文献
5.
对埕岛油田典型平台周边多年的水深地形资料进行分析对比,研究平台桩基周围冲刷过程,探讨桩柱周围形成冲刷坑的冲刷深度、几何形态和分布特征,分析其冲刷机理。结果表明,平台建成初期桩基冲刷剧烈,周围海底形成以平台为中心的盆状地形,经历近1年的时间逐步达到冲淤平衡。冲刷坑形态特征主要由水动力条件控制。 相似文献
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为减轻桩基局部冲刷对近海结构物稳定性造成的影响,采用套筒作为冲刷防护措施。在波流水槽中开展局部冲刷物理模型试验,改变波流条件、套筒相对高度和直径,记录套筒内外冲刷过程及冲刷深度发展历时,利用地形扫描仪测量冲刷后的床面形态,分析各工况下冲刷坑形态的差异,讨论影响套筒冲刷防护效果的主要因素。试验结果表明：套筒结构具有较好的防冲效果,本试验工况下,筒内冲刷深度最高可减小70%,筒内外最大冲刷深度可减小40%左右。套筒高度对筒内冲刷的影响比套筒直径更为显著,筒内最大冲刷深度随套筒高度的增大而减小。套筒直径主要影响筒外冲刷,套筒埋置于初始床面以上时,筒外最大冲刷深度随直径的增大而减小;随着套筒高度逐渐减小,直径对筒外冲刷的影响越来越小。 相似文献
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针对海上风电桩基受波浪、海流长期冲刷而造成的局部冲刷问题。本文选取海阳海上风电场为研究区,基于实测表层沉积物、长期气象、波浪和潮流数据,通过利用桩基局部冲刷经验公式计算了海阳海上风电场区桩基在不同动力条件、布设方案和环境条件下的冲刷特征,进而分析了桩基选址的考虑因素。结果表明,风电场区为局部弱冲刷区域,在1年一遇波浪情况3个常波浪方向2 m和6 m桩墩直径的条件下,场区桩墩冲刷深度最大值2.23 m,冲刷深度范围0.62～2.25 m。桩柱直径也与冲刷深度呈正相关特征,风机直径为8 m时对区域冲淤环境影响较小。此外,由于风电场区波浪对于海床具有显著影响,应采用考虑风、浪、流较全面的公式计算桩基的冲刷深度,同时在桩墩的布设位置选择时应综合考虑布设区域海床稳定性、风能大小、桩柱的直径、海床土层稳定性等特征要素。 相似文献
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针对我国南海某岛礁珊瑚砂地基上的圆形桩基础,采用N-S方程K-s模型、双向耦合方式跟踪流场中颗粒运动轨 迹的方法,对桩周珊瑚砂的冲刷规律进行了求解,分析了桩体周围流体的速度场以及桩体表面剪应力场的分布规律,同时对桩周珊瑚砂冲刷坑的形成过程进行了模拟。计算结果表明,在桩体周围形成的马蹄形漩涡和桩柱后方的尾涡作用下,桩周土体出现了较为明显的冲刷现象,涡旋的释放显著地影响着珊瑚砂地基上桩基的冲刷坑形状;而且,由于珊瑚砂颗粒密度较石英砂小,水动力作用下桩周冲刷坑更容易形成,所以实际工程中需要考虑有效的防护措施。 相似文献
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要研究波流共同作用下桩墩的基础冲刷问题,首先需要了解水流和波浪单独作用下桩墩冲刷的机理和特征。针对波、流及其共同作用下桩墩的局部冲刷问题,从流速、水深、桩径、波长、波高、相对底层流速、粒径和粒径级配等方面系统地简述了恒定流、波浪和波流作用下桩、墩局部冲刷的研究进展。根据实验资料比较了各家经典计算公式的计算结果发现我国规范65-1式计算值偏大,65-2式计算值偏小等结论。桩墩局部冲刷是一个复杂的过程,今后可以针对淤泥质海岸底床、粉沙质海岸底床、复杂桩群结构、物理模型比尺效应、非恒定水动力条件、复杂基础形式方面对波流作用下基础冲刷的最大冲刷深度、冲刷过程、冲刷范围进行研究,以弥补桩墩局部冲刷在这些方面的不足。 相似文献
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长江口南北港分汊口河段新浏河沙护滩潜堤及南沙头通道潜堤工程是典型的航道整治工程,经调查发现限流潜堤冲刷坑在两侧余排外对称分布,12 m以深等深线呈不连续坑状,南侧个别区段冲刷坑已侵入排内。基于工程地形监测和地质资料分析,通过现场水深测量、旁扫声纳扫测、潜水探摸、水文观测和三维潮流数学模型计算等手段,对限流潜堤排外局部冲刷情况和发生原因进行研究。研究结果表明潜堤排外冲刷是越顶水流长期作用所致,冲刷发展变化具有代表性,冲刷最大深度与地质条件有一定相关性。潜堤南侧护底余排边缘局部余排受外力损毁,引起排内冲刷,如进一步发展会影响堤身及结构安全,需对护底损坏部位进行修复以保证整治建筑物护底功能正常发挥。 相似文献
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波浪作用下桶形基础冲刷特性试验研究 总被引：1，自引：1，他引：0
在设计结构和考虑有效的海洋工程基础的冲刷防护工程时,了解和预测海洋结构周围的冲刷发展机理是非常重要的。通过波流水槽研究规则波作用下桶形基础的冲刷特性,试验主要考虑波高与结构尺寸对桶形基础周围局部冲刷的影响,并分析波浪冲刷过程中模型周围的时程地形、波浪作用后的冲刷坑性状、冲刷影响要素以及不同结构间的冲刷差异。结果表明:桶形基础的冲刷过程是震荡加深发展,最大冲刷深度与冲刷宽度随波高增大而增加,随上部结构直径增大而增加,最大冲刷深度位置随波高与结构尺寸变化而变化;不同结构间的冲刷坑形态与冲刷后的地形不同,最大冲刷深度相差可高达4倍;桶形基础结构直径比范围为0.2～0.5时,结构自身具有防冲刷能力。 相似文献
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This experimental study presents clear-water scour and deposition patterns around hexagonal arrays of circular cylinders in steady flow conditions. Understanding the scour processes around such configurations could facilitate the design of several hydraulic and marine engineering structures, such as bridge piers and piles. The flow alteration caused by the examined porous obstacles depends on the solid volume fraction of the obstacles and on the angle of attack of the incoming flow, due to the limited number of cylinders constituting the array. Flume experiments with erodible bed were carried out for four array densities (solid volume fractions: 0.14, 0.20, 0.32 and 0.56) under three different orientations (regular, angled and staggered configurations). The scour/deposition characteristics were obtained by means of laser scanner and the results were compared to solid cylinders of equal circumambient diameter. Different angles of attack of the incoming flow lead to different blockage ratios, which have direct impact on the scour characteristics and deposition patterns. The arrays with the higher solid volume fraction generated scour/deposition patterns similar to solid cylinder, while in the arrays with the lower solid volume fractions, local scour around the individual small cylinders became evident. Finally, considering that the load bearing capacity of a pier basically depends on the area of its cross-section, a comparison of the maximum induced scour depth and volume by the cylinder arrays and the solid cylinder with equal solid cross-sectional area is presented, in order to introduce an alternative pier configuration that induces less scour. The results showed that the array of cylinders could generate 27% less scour volume and 22% less scour depth compared to its single solid cylinder counterpart. 相似文献
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基于Flow-3D软件,建立抗拖网海床基沙土基床冲刷的三维数学模型,控制水流流速和泥沙粒径,对不同条件下抗拖网海床基周围沙土基床的冲刷进行数值模拟,并分析了抗拖网海床基最大冲刷深度随这两种因素改变的趋势。结果表明,抗拖网海床基沙土基床冲刷坑深度随海流流速增大而增加,在设定其他条件不改变的情况下,冲刷坑的加深速度随着流速增大会逐渐减缓,最终达到冲淤平衡。同时,由于海底环境复杂多变,导致模型与实际情况有一定的差异,还需在后续的研究中进一步进行优化。 相似文献
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Transport of bed sediment inside and beneath the scour protection may cause deformation and sinking of the scour protection for pile foundations. This may reduce the stability of the mono pile and change the natural frequency of the dynamic response of an offshore wind turbine installed on it in an unfavourable manner. Using physical models and 3D computational fluid dynamic (CFD) numerical simulations, the velocity and bed shear stresses are investigated in complex scour protections around mono piles in steady current. In the physical model the scour protections consisted of an upper cover layer with uniformly distributed coarse stones and a lower filter layer with finer stones. For the numerical simulations, the Flow-3D software was used. The scour protection layers were simulated with different numerical approaches, namely regularly arranged spheres, porous media, or their combinations (hybrid models). Numerical simulations with one or four layers of cover stones without filter layer were first computed. Three additional simulations were then made for a scour protection with a cover layer and a single filter layer. Finally, a simulation of a full scale foundation and scour protection was made with porous media approach.Based on the physical and numerical results, a method to determine the critical stones size to prevent motion of the base sediment is established and compared to a full scale case with sinking of scour protection (Horns Rev I Offshore Wind Farm, Denmark). It is also found that the CFD simulations are capable of calculating the flow velocities when the scour protection is represented by regular arranged spheres, while the turbulence in general is underestimated. The velocity can also be calculated using porous media flow approach, but the accuracy is not as good as for spheres. The deviation is more severe for more complex scour protections. In general, computational models provide valuable information for the prediction and design of scour protections for offshore wind farms. 相似文献
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从管道尾流区泥沙颗粒的受力平衡着手,探讨了管道冲刷的临界压力差。在此基础上,提出了一种防止或减少管道冲刷的新方法,即在管道下方安装柔性阻流器。通过物理模型试验,研究了单向恒定流及规则波作用下,柔性阻流器对管道两侧床面压力、冲刷深度的影响。试验结果表明:柔性阻流器的安装能明显减小管道两侧床面的压力差。在单向恒定流作用下,管道的冲刷深度随阻流器长度的增加而减小;当阻流器达到临界长度时,冲刷消失。规则波时,因阻流器的扰动作用,冲刷深度有所增加;但随阻流器长度的增加,其扰动作用减小,对床面的防护作用增加,因而冲刷深度减小。 相似文献
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Jenkins S.A. Inman D.L. Richardson M.D. Wever T.F. Wasyl J. 《Oceanic Engineering, IEEE Journal of》2007,32(1):78-90
A process-based, numerical, hydrodynamic vortex lattice mine scour/burial model (VORTEX) is presented that simulates scour and burial of objects of arbitrary shape resting on a granular bed in the nearshore. There are two domains in the model formulation: a far-field where burial and exposure occur due to changes in the elevation of the seabed and a near-field involving scour and transport of sediment by the vortices shed from the object. The far-field burial mechanisms are based on changes in the equilibrium bottom profiles in response to seasonal changes in wave climate and accretion/erosion waves spawned by fluxes of sediment into the littoral cell. The near-field domain consists of one grid cell extracted from the far-field that is subdivided into a rectangular lattice of panels having sufficient resolution to define the shape of the object. The vortex field induced by the object is constructed from an assemblage of horseshoe vortices excited by local pressure gradients and shear over the lattice panels. The horseshoe vortices of each lattice panel release a pair of vortex filaments into the neighboring flow. The induced velocity of these trailing vortex filaments causes scour of the neighboring seabed and induces hydrodynamic forces on the object. Scour around the object and its subsequent movement into the scour depression contribute to burial, while far-field changes in local sand level may increase burial depth or expose the object. Scour and burial predictions of mines and mine-like objects were tested in field experiments conducted in the nearshore waters off the Pacific coast of California at Scripps Pier, the Gulf Coast of Florida at Indian Rocks, and off the Atlantic coast of Massachusetts at Martha's Vineyard. Model predictions of mine scour and burial are in reasonable agreement with field measurements and underwater photographs. 相似文献