EFFECTS OF FLOW INTENSITY, OBSTACLE ALIGNMENT AND CROSS-SECTION GEOMETRY ON SCOUR AT BRIDGE ABUTMENTS     

A. H. CARDOSO  J. S. SANTOS  M. ROCA EFFECTS OF FLOW INTENSITY  OBSTACLE ALIGNMENT  CROSS-SECTION GEOMETRY ON SCOUR AT BRIDGE ABUTMENTS A. H. CARDOSO  J. S. SANTOS  M. ROCA EFFECTS OF FLOW INTENSITY  OBSTACLE ALIGNMENT  CROSS-SECTIO 《国际泥沙研究》2002,17(2)

1 INTRODUCTION Local scour at bridge piers and abutments has long concerned engineers. Scour depth estimation has attracted considerable research interest and activity, and a number of prediction methods exist at present (see, e.g., comprehensive lists of predictors given by Melville and Colleman, 2000). Several studies have been completed since the 1950s for the particular case of scour at bridge abutments. Since the beginning of the 1980s, the University of Auckland, New Zealand, …  相似文献   

Multibeam bathymetric and sediment profiler evidence for ice grounding on the Chukchi Borderland, Arctic Ocean   总被引：1，自引：0，他引：1  

Martin Jakobsson  James V. Gardner  Larry A. Mayer  Jan Backman  Brian Calder  Barbara Kraft 《Quaternary Research》2005,63(2):150-160

Multibeam bathymetry and 3.5-kHz sub-bottom profiler data collected from the US icebreaker Healy in 2003 provide convincing evidence for grounded ice on the Chukchi Borderland off the northern Alaskan margin, Arctic Ocean. The data show parallel, glacially induced seafloor scours, or grooves, and intervening ridges that reach widths of 1000 m (rim to rim) and as much as 40 m relief. Following previous authors, we refer to these features as “megascale glacial lineations (MSGLs).” Additional support for ice grounding is apparent from stratigraphic unconformities, interpreted to have been caused by ice-induced erosion. Most likely, the observed sea-floor features represent evidence for massive ice-shelf grounding. The general ESE/WNW direction of the MSGLs, together with sediment, evidently bulldozed off the Chukchi Plateau, that is mapped on the western (Siberian) side of the plateau, suggests ice flow from the Canada Basin side of Chukchi Borderland. Two separate generations of glacially derived MSGLs are identified on the Chukchi Borderland from the Healy geophysical data. The deepest and oldest extensive MSGLs appear to be draped by sediments less than 5 m thick, whereas no sediment drape can be distinguished within the resolution of the sub-bottom profiles on the younger generation.  相似文献   

EXPERIMENTAL STUDY ON BED SCOUR IN A 90°CHANNEL BEND     

Masoud GHODSIAN  S. Kamal MOUSAVI 《国际泥沙研究》2006,21(4)

The special feature of bend flow leads to scouring of the bed and bank. Various parameters like flow depth, flow velocity or discharge, geometry of bend and characteristics of bed material may affect the scour process. Experiments were carried out to study the effect of some important parameters on bend scour under clear water condition. Experiments were conducted in a 0.6m wide and 0.7m high flume with 90 degree bend. The lateral variations of bed slope were studied. The maximum depth of scour was correlated to densimetric Froude number, relative bend radius and relative depth of flow.  相似文献   

IMPACTS OF DIMENSION AND SLOPE OF SUBMERGED SPUR DIKES ON LOCAL SCOUR PROCESSES - AN EXPERIMENTAL STUDY     

Daxian FANG Jueyi SUI Ronald W.THRING Hongya ZHANG 《国际泥沙研究》2006,21(2):89-100

1 INTRODUCTION In alluvial streams bed scour often occurs if the sediment load is less than the transport capacity of the flow. Two types of scour are identified, namely local scour and channel bed scour. Channel bed scour can be further classified accord…  相似文献   

桥墩冲刷坑的三维流场测量与数值模拟          下载免费PDF全文

孙东坡  杨慧丽  张晓松  王二平 《水科学进展》2007,18(5):711-716

采用Sontek公司声学多普勒测速仪(ADV)对有拦沙坝防护的模型桥墩附近流场进行了精细测量,对桥墩冲刷坑内三维流速分布进行了分析,给出了冲刷坑内三维紊动特征量的分布,分析研究了有拦沙防护坝时桥墩局部冲刷的三个新特点,提出了拦沙坝的适用条件。另外,还采用有限体积法(FCVM)对桥墩附近流场进行了三维水流数值模拟,与ADV实测数据进行了对比验证,结果比较吻合。利用测量与模拟成果分析了墩前三维流速分布规律及对桥墩局部冲刷的影响,对研究复杂边界桥墩流场结构与局部冲刷计算有参考价值。  相似文献   

北羌塘坳陷冬曲地区上三叠统巴贡组扇三角洲沉积特征   总被引：3，自引：1，他引：2       下载免费PDF全文

陈浩  孙伟  占王忠  何磊 《沉积与特提斯地质》2018,38(4):97-103

北羌塘坳陷冬曲地区上三叠统巴贡组为一套碎屑岩沉积,在垂向上具有两个向上变粗的充填序列。根据沉积体产出形态和叠置序列、岩石组合与结构、沉积构造及流体性质等沉积特征,确定该套沉积体为扇三角洲相沉积,进而可划分出扇头、扇中、扇尾3个亚相。发育底冲刷构造、粒序层理、平行层理、交错层理等,表明其流体性质既有重力流又有牵引流特征。通过该套扇三角洲沉积体的认识,对研究该区古构造背景、沉积环境及油气地质条件等具有重要意义。  相似文献   

层状土场中冲刷作用下部分埋置单桩动力响应分析     

马建军  韩书娟  高笑娟  李达  郭颖 《岩土力学》2022,43(6):1705-1716

桩周土场受冲刷作用的变化是部分埋置单桩结构失效的主要原因之一。工程中土场多呈层状,此类场地中桩基的力学特性研究日益受到关注。为精确揭示冲刷作用对层状土场中部分埋置单桩动力响应的影响,基于改进Vlasov地基模型,利用Hamilton原理建立层状土场中横向受荷单桩的动力学模型。利用有限差分法求解受冲刷作用单桩的固有频率,实现对冲刷作用下土−结构相互作用系统的准确建模,进而用Green函数法求得单桩受迫振动的解析解。通过数值计算和参数分析,研究了层状土场的物理特性对受冲刷作用部分埋置单桩动力响应的影响。结果表明：基于改进Vlaosv地基模型建立的层状土场中部分埋置单桩动力学模型可精确预测冲刷作用对桩基动力学特性的影响。随冲刷程度加剧,层状土场中单桩的第一阶固有频率显著降低,改进Vlasov地基模型中各层土体的地基反力系数均减小,剪切系数则增大。当冲刷至非埋置段桩长 （ 为桩长）时,部分埋置单桩在动荷载作用下出现横向失稳现象。随底层土体厚度增加,各冲刷等级下单桩的第一阶固有频率均增大。如果第1层土的弹性模量增大了约0.43倍、1.14倍、1.86倍,则冲刷等级为0时单桩第一阶固有频率分别增大了约8.9%、19.5%、27.1%。  相似文献   

Temporal evolution of scour at bridge abutments in compound channels     

《国际泥沙研究》2022,37(5):662-674

Bridge abutment-induced sediment scour in compound river channels is time-sensitive during floods, and, thus, estimating the scour rate has significance in design. In the current study, large-scale laboratory experiments were done to examine the influence of multiple factors on scour evolution, including channel geometry, bed mobility (clear-water or live-bed), and lateral (embankment intrusion) and vertical (deck submergence) flow contractions. A new method is applied for scour measurement and determination of characteristic scour trends. Results show that the non-dimensional time scale is related to flow intensity and may peak before reaching the clear-water scour threshold; the corresponding equations also are derived. It is found that the use of scour countermeasures has a significant impact on the scour rate, and the existing equations for unprotected abutments have limitations. Under clear-water conditions, the scour rate is closely related to the overall flow contraction, which can be better reflected by the ratio of the approaching unit discharge to that at the bridge section. Specifically, the effect of vertical flow contraction on scour rate is more dominant than other factors. Two scour rate curves are derived to suit different structural and flow contraction types for clear-water scour. In contrast, the live-bed scour rate data are generally consistent and fall in a narrow band, showing less dependence on other factors. Finally, a new design approach is established to estimate the time scale and scour rate using the new equations proposed in this paper.  相似文献   

苏通长江公路大桥桥区河床抗冲性能试验研究   总被引：1，自引：0，他引：1  

洪大林 谢瑞张思和  唐存本 《海洋工程》2003,21(4):91-96

针对交通、水利工程中遇到的实际问题，采用现场原状土取样，并通过封闭管道水力试验，得到原状土起动的临界切应力及冲刷率，并通过公式换算得到原状土的起动流速，这一方法可用来确定物理模型试验中动床模型设计参数，并可为设计部门提供科学依据。  相似文献   

Numerical Simulation of Wave Scour Around A Large-Scale Circular Cylinder     

ZHAO  Ming 《中国海洋工程》2002,16(4):513-523

A numerical model is developed for estimation of local scour around a large circular cylinder under vvave action. The model includes wave diffraction around structures, bed shear stress calculation inside the vvave boundary layer and topo-graphical change model. The vvave model is based on the improved Boussinesq equations for varying depth. The vvave boundary layer is calculaled by solving the integrated momentum equation over the boundary layer. The bed shear stress due to streaming, an important factor affecting the sediment transport around a large-scale cylinder, is calculated. The Lagrangian drift velocity is included in calculation of the suspended sediment transport rates. The model is implemented by a finite element method and the results from the present model, which agree well with experimental data, are com-pared vvith those from other methods.  相似文献