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海上风电基础局部冲刷会影响风电结构的稳定,对海上风电的安全运行至关重要。以四腿群桩导管架基础为研究对象,对潮流条件下基础局部冲刷开展试验研究。试验结果表明：0°水流条件下,最大冲刷深度为1.05倍桩径;45°水流条件下,最大冲刷深度为0.97倍桩径。并探索了新型蜂巢结构在群桩基础防冲刷中的应用,设计了蜂巢格室防护方案,发现在蜂巢防护情况下,两个流向作用于四腿群桩基础时最大冲刷深度仅为无防护情况下的27.3%和25.9%,表明蜂巢格室在海上风电基础的冲刷防护方面具有良好效果,在实际工程中具有较大的应用潜力。 相似文献
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单向流条件下单桩桩周冲刷过程特征试验研究 总被引：2，自引：1，他引：1
水流引起桩基周围地基冲刷是海洋工程中的经典课题,由于问题涉及流体动力学和土力学的交叉内容,加之试验技术和计算能力的限制,这一冲刷过程仍有很多方面尚待进一步厘清。开展10组室内水槽试验,研究了不同水深情况下定床和动床冲刷时单桩桩周局部冲刷深度的发展过程。在试验过程中,通过模型桩内放置摄像机实时监测桩周冲刷深度变化,得到桩周冲深边界及最大和最小冲深方位随时间的变化曲线。试验研究发现这一冲刷过程主要特征为:局部冲刷首先发生在桩(侧)前方并逐渐向桩周扩展,而桩后则先发生淤积后再冲刷;水深越大,流速越大,桩后淤积现象持续时间越短,桩周冲刷发展迅速、均匀,但达到稳定所需时间越久;桩周最大、最小冲深点首先分别位于桩的侧前方、桩后区域,随着试验进行会发生转变或波动。 相似文献
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为研究水流作用下斜桩周围局部冲刷特性及流场变化并掌握斜桩同垂直桩的差异,本研究在不同流速条件下开展了包含反斜桩、垂直桩、正斜桩等多种工况的水槽试验,测量分析了斜桩的冲刷历时曲线、床面形态、沿程流速分布、最大冲刷深度等数据.结果表明:清水条件下斜桩周围局部冲刷坑及桩后沙丘尺度明显减小;斜桩桩前最大冲刷深度随倾角的增加而逐... 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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小尺度群桩应用广泛,一直是学者研究的重点,小尺度有别于大尺度桩柱,由于桩柱周围存在漩涡的脱落,使得受力特性复杂。以往的研究过程中,波浪主要采用单向不规则波浪,并且试验模型多以两桩或三桩组成的群桩结构为主,桩数相对较少。多向不规则波与群桩结构的作用特点有别于单向不规则波且研究较少。通过物理模型试验,针对多向不规则波对于9桩桩排群桩结构的作用进行了研究。首先综合考虑KC1/3数和相对桩径的影响,提出以参数KCLD 1/3数来衡量群桩的效应,并分析了正向力与横向力随着参数KCLD 1/3数和相对桩距的变化关系,研究了群桩中不同桩位桩柱波浪力的变化规律和方向分布宽度对于群桩波浪力的影响。研究结果表明,群桩中各桩的正向力随着方向分布标准差的增大而减小,而横向力在相对桩距较大时随着方向分布标准差的增大而增大,同时群桩中不同位置桩上的波浪力具有较大的差异。 相似文献
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针对水下桩墩的局部冲刷问题,提出一种适用范围广、防冲促淤效果显著的防护措施。该防护措施把一种相对密度略大于水、几何特征特殊的中性网格结构完全覆盖在冲刷坑或可能出现冲刷坑的床面上,以减弱冲刷坑内水动力,促进泥沙落淤,达到减轻局部冲刷的目的。通过数值模拟和水槽试验探讨了中性网格结构对圆桩周围冲刷坑内水动力及床面形态的影响,并研究了网孔尺寸对防冲促淤效果的影响规律。结果表明：该中性网格结构能显著减小局部冲刷坑内的流速,有效抑制局部冲刷,且对桩前来流来沙的影响微弱。孔径比7.7的网格防护结构可以使无黏性沙床上圆桩的局部冲刷深度减少92%,已存在的冲刷坑则可被修复73%。这些研究成果为桩墩局部冲刷防护提供一种新的思路。 相似文献
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波浪作用下桩桩周围局部冲刷研究 总被引：7，自引：0，他引：7
通过系统的物理模型试验,考虑波高、周期、水深、泥沙粒径、桩柱直径等影响因素,研究桩柱周围的局部冲刷形态、尺度高。分析了桩柱周转局部产中刷的三种基本类型,得出最大冲刷深度随波数的变化规律,提出了最大冲刷黉度的计算方法。 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
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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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Bridge scour is recognized as one of the key factors that causes structure failures, which in turn leads to economic and life loss. In this study, flume tests of four typical arrangements of pier groups embedded in sand under steady clear water conditions were carried out to observe the process and maximum depth around piles of scour. The investigation included single pile, tandem piles, side-by-side piles, and 3 × 3 pile groups. Different conditions including different pile spacing, flow velocity, and water depth are considered. Moreover, the evaluation of design methods from the United States, New Zealand, and China was analyzed and compared through experimental and mathematical methods. The experimental results show that shielding and jetting effects are obvious in pile groups, which become less obvious with the increase of pile spacing. The dynamic process of scour around single pile and pile groups are quite different. Meanwhile, most of the predicted scour depths by these equations tend to be much larger than those from field data, which may lead to overdesign and consequently high construction cost. In addition, data from this study and some laboratory experiment data from previous work were used to derive the correction factors of a new scour prediction equation, which can be used to estimate the scour in a sand bed and agree well with the observations. 相似文献
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Pile groups are frequently used to support bridge decks. Scour in the vicinity of piles is the main cause for the bridges failure. In this research, to address the effects of uniform and nonuniform pile spacing on the equilibrium scour depth, laboratory experiments were carried out under steady clear-water conditions. For this purpose, scour depth produced by pile group with various pile spacing and arrangement was investigated using a laboratory flume. Flume bed was covered by uniform sediments with a median size of 0.9?mm and 0.2?m thickness. Flow discharge and velocity as well as scour depth were recorded in each experiment and the data were analyzed. The results showed that the pile spacing influences the local scour depth and with increase in uniform and transverse (perpendicular to the flow) spacing, the maximum scour depth was reduced. The pile spacing variation in line with the flow has a minor effect on scour depth. In addition, the pile spacing perpendicular to the flow was with the most influences on scour depth. The results of this research can be used by engineers to optimize the design of bridges. 相似文献
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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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Most offshore and coastal structures are supported by pile foundations, which are subjected to large lateral loads due to wind, wave, and water currents. Water currents can induce scouring around piles that reduces lateral capacity and increases lateral deflection of a pile. Current design methods mostly consider the complete removal of soil layers around piles by scouring. In reality, however, scouring creates scour holes at different shapes, sizes, and depths. Their effects on the behavior of laterally loaded piles are not well investigated. A numerical model of a single pile in soft marine clay was first calibrated against field test data without scour. Then several key factors of scour were analyzed, such as the depth, width, and slope of the scour hole and the diameter and head fixity of the pile. The relationships of the ultimate lateral capacity of the single pile with the depth, width, and slope angle of the scour hole were obtained. The numerical results show that the scour depth had more significant influence on the pile lateral capacity than the scour width. In addition, the pile with a free head was more sensitive to scour than the pile with a fixed head. 相似文献
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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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The scour hole around a pile will reduce the capacity of a laterally loaded pile. The strain wedge model is capable to derive a p–y curve for the analysis of a lateral loaded pile on a nonlinear Winkler foundation. To improve and extend the ability of the strain wedge method, a modified strain wedge (MSW) method is developed, in which a nonlinear lateral deflection of the pile is assumed to describe the varied soil strain distribution in the passive wedge. And then by treating the soil weight involved in the strain wedge as a vertical load at the bottom of the scour hole, an equivalent wedge depth is obtained to consider the effect of scour hole dimensions on the response of laterally loaded piles in sand. The validity of the MSW model is proved by comparisons with a centrifuge test without scour. And its applicability in the problem of a pile with scour is performed by a comparison with a model test and a FE analysis. The analysis shows the pile displacement at the pile head with scour can be obtained by multiplying the corresponding deflection without scour with an amplification factor related to scour depth at large load level. 相似文献