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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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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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大型涉水群桩桥基局部冲刷特性试验研究 总被引：2，自引：0，他引：2
利用正态宽水槽研究梅花形大型涉水群桩基础的局部冲刷特性,得到最大冲深、最深点位置以及桩群内垂向和顺水向的冲刷形态,并与常规形群桩布置引起的冲刷进行了试验对比.其中梅花形群桩局部冲刷的特性和试验结果在苏通长江大桥建设中得到较好地验证. 相似文献
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The scour behavior of cushioned caisson constructed on reinforced ground, which is used to support superstructure constructed in deep water in seismic zones, was investigated by experimental and numerical methods. Flume tests under nine different flow velocities between 18 and 48?cm/s were performed based on hydraulic similarity design. Complementary numerical simulations were also conducted for the flow velocities ranging from 16 to 46?cm/s. Five typical working modes of the foundation under erosion, namely, ideal working, well working, edge failure, shear failure, and total failure, are analyzed together with their potential impacts on seismic-designed foundation. The critical shear stress, local flow structures, and streamlines were used as the key factors to analyze the change of bed materials and the scour characteristics. Fluid–solid interaction model was built by computational fluid dynamics with sediment transport model, and k–ε turbulent model has been implemented to describe the turbulence in the fluid phase typical of scour process. The mechanisms of two possible failure models for the foundation layer elements were identified, based on which recommendations were provided for scour protection to ensure the integrity and performance of seismic-designed foundations. The integrated computational model and model experiments also demonstrate a framework to understand the local scour mechanism for the cushioned caisson on reinforced ground. 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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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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Local scour around a bridge pier is an important pm‘mneter for the design of a bridge. Compared with the local scour in a mono-directional current, the local scour in a tidal current has its unique characteristics. In this paper, several aspects of local scour around bridge piers in tidal current, including the scour development process, the plane form of a scour hole and the maximum scour depth, are studied through movable bed flume experiments. 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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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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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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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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A laboratory study of local scour at complex piers under steady clear-water conditions is presented. The term complex piers is used to define a bridge pier comprising of a column, pile cap, and pile group. Comprehensive data over the full range of possible pile cap elevations for complex piers with different geometries were obtained using five complex pier models, which were scaled down from existing bridges in Malaysia. The data are used to evaluate existing methodologies for characterizing the effective width of complex piers with varying pile cap location relative to the undisturbed streambed. The effect of pile cap location on scour depth is also addressed. To improve the predictions of local scour at complex piers, the new data and some previous data are used to propose a new method to predict local scour depth at complex piers. 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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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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桥墩基础冲刷是桥梁毁坏的重要因素,是桥梁基础设计的关键指标之一。目前国内外对于桥墩基础在复杂动力条件下冲刷深度的研究常采用物理模型试验方法,利用正态系列模型方法,在波流水槽中研究了水流、潮流和波流共同作用下青州航道桥索塔基础周围流态变化和局部冲刷特征。研究结果表明,桥墩最大冲刷深度和冲淤范围与水流流速、桥墩轴线与水流夹角和波浪等因素有关;在潮流最大流速和恒定流流速一致情况下,桥墩局部冲刷深度达到平衡后,将会达到与恒定流基本一致的最大冲深;波流共同作用下的最大冲刷深度比恒定流增加10%左右。设计桥墩形状在100年一遇水流和波浪共同作用下桥墩基础局部最大冲刷深度为13.7 m。 相似文献
