Laboratory Investigation of Stilling Basin Slope Effect on Bed Scour at Downstream of Stepped Spillway: Physical Modeling of Javeh RCC Dam

Stepped spillway and stilling basin are one of the most important energy dissipation structures. Eventhough, most of energy dissipated by these structures, but in skimming flow, the upstream flow motion is nonaerated and the residual energy capable to destroyed structures during floods. In this study, effect of stilling basin slope on bed scour, downstream of Javeh dam was investigating. Experiments performed in hydraulic structures laboratory of the University of Kerman with six different discharges (5, 7, 13, 17, 25 and 30 l/s.m) and five various stilling basin slope (0.02, 0.01, 0, ?0.01 and???0.02). The parameters such as maximum scour depth (d_s), flow velocity (in three point), water depth on upstream and downstream of stepped spillway and stilling basin, the distance of the maximum scour depth to sill (L_s) and the gheometery of scour hole measured. Result shown that when stilling basin slopes was 0.02, the average of maximum relative scour depth, 47% Increased and in ?0.02, 52.2% Decreased. In addition, the distance of maximum scour depth until stilling basin increased by increasing and decreased by decreasing the stilling basin slope.

     

Scour due to rock sills in straight and curved horizontal channels

Scour characteristics and morphologies downstream of rock sills due to channel curvature have been analyzed at the hydraulic laboratory of the University of Pisa. Two series of experiments have been conducted. The first series included tests on scour downstream of rock sills in straight channel. Three different channel bends with different lengths were studied in the second test series. All experiments have been carried out in clear water condition. The results showed that the tailwater depth plays an important role on scour characteristics. In addition, it was experimentally proven that the stream curvature affects the morphology and the maximum scour depth, i.e., an increase of the bend radius causes a decrease in the value of the maximum scour depth. Finally, three scour morphology types have been distinguished. Useful empirical relationships have been proposed in order to evaluate the main features of the scour geometry.     

消能工在白杨河水库的联合应用

针对白杨河水库枢纽工程原设计方案消力池尺寸不足,下游护坦流态不良、冲刷严重的问题,进行了四种不同修改方案的试验研究。通过对原方案及修改方案水流流态的观察,水深、流速、消能率等方面的测量计算,推荐采用“阶梯式溢洪道＋消力墩”的联合消能方案。试验表明,阶梯式消能工可以消除水流的大部分能量,减小消力池及下游护坦的消能负荷。将...     

Scour process caused by multiple subvertical non-crossing jets

The scour process induced by plunging jets is an important topic for hydraulic engineers. In recent decades, several researchers have developed new strategies and methodologies to control the scour morphology, including different jet arrangements and structures located in the stilling basin. It has been found that multiple jets can cause less scouring than single plunging jets. Based on this evidence, this study aimed to investigate the equilibrium morphology caused by multiple non-crossing jets. A dedicated laboratory model was built and experimental tests were carried out under different combinations of jet inclination angles, by varying the tailwater level and the virtual crossing point location, which was set below the original channel bed level. It was experimentally shown that the equilibrium scour morphology depends on the jet discharge, the differences in non-crossing jet inclination angles, the downstream water level, and the distance of the virtual crossing point from the original channel bed level. In particular, the last parameter was found to be one of the most influential parameters, because of the resulting flow patterns inside the water body. Furthermore, the analysis of experimental evidence allowed for a complete and detailed classification of the scour hole typologies. Three different scour typologies were distinguished and classified. Finally, based on previous studies, two novel relationships have been proposed to predict both the maximum scour depth and length within a large range of hydraulic and geometric parameters.     

Scour downstream of cross-vane structures

Cross-Vanes are hydraulic structures used to stabilize the riverbed and control the grade for river restoration. Scour downstream of Cross-Vane structures depends on the shape of the structure, the bed material and the river hydraulic conditions. This paper aims to predict the maximum scour depth and classify the scour morphology. Two series of experiments were carried out. In the first series, two types of structures, which are I-shape and U-shape structures have been studied in a horizontal channel. In the second series of experiments, riverbed slopes of 1%, 2.5% and 5% were tested. For each type of structure, three heights in different hydraulic conditions including densimetric Froude numbers and drop heights were tested. Results show, that the ratio between the length of the structure and the channel width is one of the most important non-dimensional parameter to classify the scour. New analytical functions have been derived from dimensional analysis to predict the maximum scour depth, the maximum length of the scour, location of the maximum scour depth and the maximum development of the scour width. All the experiments were conducted in clear water conditions. Based on dimensional analysis and using all collected data new equations have been obtained. Scour morphology downstream of Cross-Vane structure was classified in different scour patterns based on different flow hydraulic conditions, structures geometries and the ratio between the maximum length of the scour and the channel width.     

老口航运枢纽泄水闸坝消能防冲设计

老口航运枢纽工程是一座以航运、防洪为主,结合发电,兼顾为改善南宁市水环境创造条件的综合性枢纽.泄水闸坝的消能防冲设计应满足船闸下引航道和电站正常运用的要求,减轻对下游河床的冲刷.通过水工模型试验的验证,泄水闸坝的闸下消力池消能效果基本满足设计要求.     

长沙坝水库除险加固设计

浆砌石坝尤其是浆砌石拱坝的除险加固,目前经验较少。本文以长沙坝水库《大坝安全鉴定报告书》为基础,利用原设计资料,对大坝、消力池、冲砂孔与放水孔设施、左岸危岩体、防汛公路等项目的加固进行了方案比较,推选出适宜的加固方案,并据此进行加固设计。本文重点介绍了长沙坝水库主要建筑物加固设计,可供同行参考。     

平原区水闸闸下消能防冲与闸门控制运行

针对平原区水闸闸下消能防冲与闸门控制运行的特点,基于水力学理论分析,导出了消力池最大深度的计算公式。以沙颍河郑埠口水利枢纽工程为例,确定消力池的设计方案。根据消能防冲应满足的水流条件,由系列模型试验资料绘制了闸门控制运行曲线图,继而依据该图制定了满足消能防冲要求的闸门控制运行方式。应用结果表明,采用该消力池方案设计并按此闸门控制方式运行,能很好地满足消能防冲要求。     

隔河岩工程水力学安全监测技术及成果分析

 1998年汛期隔河岩水利枢纽观测部位为深孔、表孔 及消能工。其观测内容包括流态、时均压力、空化噪声、流速、雾雨。观测结果表明：该工程泄洪表孔、深孔、消力池及辅助消能工的各项水力学特性基本良好。泄水建筑物过流面、一级池两边岸坡均无蚀损，二级消能工上的消力墩、差动坎等均基本完好无损，但1998年2 月抽干检查发现消力池有局部磨损，左岸隔流堤护岸在1998年泄洪过程中发生局部坍滑。由于集中坝身泄洪，泄洪时雾化现象较严重，故须采取措施，以确保工程安全运行。将部分原 型观测资料与模型试验资料和计算值作了对比，总趋势和数值基本一致。     

多级连续消力池水跃的水力特性模型试验

以低弗劳德数、大单宽流量的安谷水电站为例,对不同方式形成多级水跃的消力池进行了系列水工模型试验,研究了不同方案形成的多级水跃的水力学特性。试验结果表明:采用多排消力墩方式形成多级消力池,其消能率虽有保证,但消力墩布置形式对池内流态影响较大,对不同单宽流量工况适应性不好,特别是单宽流量大时难以形成多级水跃;采用圆弧进口连续坎式消力池大幅度改善了流态,但仍未能形成两级水跃;采用跌坎进口连续坎式形式的两级浅水垫消力池,在很大流量范围内均形成明显的两级水跃流态,消能效果理想,池内临底流速和出池流速均比其他方案低,结合下游的反坡护坦,间接抬高了下游水位,使得出池水流平顺,且结构简单,施工方便。     

共青河泄洪闸除险加固工程试验研究

共青河泄洪闸下游河道由于人为过量挖沙导致下游河床下切、水位降低 ,泄洪闸泄洪造成了下游左堤岸决堤。共青河泄洪闸除险加固工程方案的试验研究表明 ,在泄洪闸原消力池下游设置二级消力池 ,能较为妥善地解决消力池出流与下游河道水流衔接过渡的问题。     

电厂排水口消力池优化试验研究

结合某电厂排水口工程进行了水力模型试验，主要研究了消力池的水力特性及其下游的防冲措施，旨在改进原设计方案，为优化设计提供依据，针对原设计的扩散式消力池中因扩散角过大造成的池内流态不佳、出流不均的问题，提出在池中前端设置适宜的消力槛，能明显地改善池内流态、均化出流；并通过试验对消力槛的设置参数及体型进行了优化，将消力池长度缩短后的池内设槛方案作为推荐方案，消力池下游防冲措施研究中，对设置斜坡式海漫或防冲槽的防护方案分别进行了泥沙冲刷试验，结果验证了消力池改进方案的有效性和斜坡式海漫防护措施的安全性，提供了防冲槽抛石防护措施中可采用的一些设计参数，本研究成果可供类似排水口工程设计时参考。     

浅谈高坝洲水电站大坝消能池水下检查及修补工程

介绍了高坝洲水电站大坝消能池水下检查及修补的技术工艺。大坝消能池包括表孔戽式消能池和深孔带雷伯克尾坎的底流消能池,分别承担表孔、深孔泄流消能,以保护下游河床、岸坡和大坝坝趾不被淘刷,保证洪水安全下泄。为及时了解水下消能池的工程状况,须定期对下游消能池进行水下检查,必要时进行修补处理。     

涝河渠化河道治理

涝河发源于秦岭北麓,系渭河支流。70年代初,对其中、下游河段曾进行过渠化治理,但每逢洪水,坍塌毁损工程仍有发生。通过模型试验又作了如下改建治理:运用梯级溢流坝调整控制河床平衡比降,坝下游设消力池,合理确定河床宽度,使河道流态改善,流速分布均匀,制止了水毁工程的发展。     

水电站水闸闸门改造设计实例分析

低水头水闸结构中经常会用到底流式消能工程,该工程对于消力池尺寸的控制比较复杂,对闸门开启高度和下游水位深度有很大要求,同时启闭机的正常使用也是影响水位的关键因素,所以如何设计一个合理、简易操作的闸门型式是提高水电站工程效率的重要方面。文本通过笔者参与的某水电站闸坝闸门改造设计为例,从闸坝消力池的尺寸控制、二台机运转的正常运用等方面进行分析,总结更为合理、有效、操作便利的闸门型式,以供广大读者参考。     

莲花台水电站宽尾墩联合消能工的应用研究

针对莲花台水电站泄洪建筑物泄量大、单宽流量大、河床易冲刷的特点,通过模型试验对原设计的挑流消能方案和Y型宽尾墩+戽式消力池联合消能工方案进行了对比研究.试验结果表明,联合消能工方案在典型工况下消能充分,下游河床及电站尾水护坦末端冲刷大为减轻,出池水流衔接平顺,下游河道流态明显改善.该研究成果对类似工程有借鉴意义.     

用岩块放大法模拟岩基冲刷的试验研究

 丹江口堰顶溢流坝下游河床,由于受基岩构造特性的影响,产生较大的冲刷。为了论证原型观 测成果,模型利用岩块放大法,采用4种不同粒径松散碎石的动床试验,对坝下游河床的冲刷, 进行了复演试验。试验表明:冲坑深度当模型动床碎石换算粒径比原型 冲坑冲出的块石粒径大,(约2.25倍)时,原型和模型能吻合,但冲刷坑的形状, 两者不尽相同。     

用岩块放大法模拟岩基冲刷的试验研究

丹江口堰顶溢流坝下游河床 ,由于受基岩构造特性的影响 ,产生较大的冲刷。为了论证原型观测成果 ,模型利用岩块放大法 ,采用 4种不同粒径松散碎石的动床试验 ,对坝下游河床的冲刷 ,进行了复演试验。试验表明 :冲坑深度当模型动床碎石换算粒径比原型冲坑冲出的块石粒径大 ,(约 2 .2 5倍 )时 ,原型和模型能吻合 ,但冲刷坑的形状 ,两者不尽相同     

顶山隧洞进出口水工模型试验研究

通过对顶山隧洞进出口水工模型试验研究,验证隧洞进出口各种工况下的水流流态和消力池的消能效果及水流对下游渠道可能产生的冲刷影响;试验测得隧洞进出口水流流态基本平稳,隧洞出口的消力池末端流速不大,不会对下游渠道产生大的冲刷破坏。