西藏扎拉水电站水库泥沙对电站运行影响试验研究

为了分析西藏玉曲河扎拉水电站运行后水库泥沙对电站取水发电产生的影响,基于扎拉电站整体河工模型试验成果,对扎拉电站运用50 a水库泥沙淤积过程,泄水建筑物及电站引水口前泥沙淤积分布、淤积高程,电站过机泥沙特性进行了试验研究。结果表明:水库运用50 a末,库区泥沙基本达到冲淤平衡,水库淤积总量约占总库容的66.45%;坝前泥沙淤积高程基本与底孔进口底高程齐平,对底孔泄流排沙影响不大;电站引水口前形成较明显的冲刷漏斗,引水渠淤积对电站正常引水影响不明显;电站过机泥沙,在水库运用初期没有0.1 mm的粗沙,在水库运用50 a末,遇常年含沙量洪水,过机泥沙中粒径0.1 mm的粗沙占过机总沙量的3.2%。建议下阶段进行优化水库调度,提高水库排沙效率的研究,进一步减少水库泥沙淤积,减轻泥沙对机组的磨损。     

大古水电站坝前排沙运行方式与排沙漏斗形态

为给实际工程排沙设施的设计和布置提供依据,基于1∶60整体模型,根据淤积泥沙扬动流速相似原理,试验研究大古水电站2条排沙廊道和1个底孔在不同运行方式下坝前库区的排沙效果和排沙漏斗形态。结果表明:排沙洞开启顺序对最终排沙效果影响不大;深水条件下,坝前排沙漏斗形态主要受泥沙特性决定,非黏性沙的排沙漏斗坡度接近于淤积泥沙水下休止角;大古水电站排沙设施的设计方案具备保证电站进水口"门前清"的条件。     

水库坝前及泄水底孔内泥沙淤积形态断面模型试验研究

新疆地区水库具有多泥沙特点,是造成水库库区水位抬高、库容降低的主要原因。文章以新疆克孜尔水库建设为工程实例,在水流运动、悬沙淤积相似条件基础上,计算出水库坝前及泄水底孔内泥沙淤积形态断面模型比尺,通过建立的试验模型对水库坝前及泄水底孔内泥沙淤积形态断面进行分析,对指导水库汛期排沙及大坝检修有重要作用。     

小浪底工程2018年高含沙水流泄洪排沙运用实践

小浪底工程2018年度进行了低水位、大流量、高含沙量泄洪排沙运用,库区泥沙淤积三角洲顶点向坝前推移了8.65 km,顶点高程降低了8.49 m,排沙比达238%,减少了库区泥沙淤积、调整淤积形态。同时在泄洪排沙运用中,出现了泥沙淤积造成闸门启闭困难、高含沙水流对闸门及流道磨蚀严重、泥沙在线监测设施不足、发电运行方式调整等问题。针对低水位高含沙水流泄洪排沙运用,需进一步完善泥沙监测应急预案,提高泥沙淤积的预测预判能力;进一步优化孔洞运用方式,完善闸门操作规程,减少高含沙水流对闸门淤堵及磨蚀的影响;开展高含沙水流相关问题的研究,加强设施设备维护保养力度,确保枢纽安全稳定运行;小浪底水库进入拦沙后期第一阶段,水库排沙比增加,水库坝前淤积增加,需进一步加强小浪底水库高含沙水流运动研究,分析水库泄洪建筑物排沙机理,为水库安全生产提供技术支持。     

大化水电站排沙廊道设计评述

大化水电站位于红水河中游。红水河是广西含沙量最大的一条河流,汛期含沙量较大以悬移质为主。坝址实测最大含沙量9公斤/立方米,多年平均含沙量0.73公斤/立方米,多年平均输沙量4590万吨。鉴于大化电站下游已建成运行的恶滩水电站枢纽第一期工程泥沙淤积严重,因此,本工程需考虑排沙问题。要求在水电厂房各机组的进水口前缘设置排沙廊道,做到“门前清”,以减少过机泥沙量及防止泥沙淤堵厂房进水口。     

排沙漏斗悬移质泥沙运动数值模拟

排沙漏斗是一种利用立轴旋涡实现水沙分离的二级排沙设施。为了探明排沙漏斗悬移质泥沙运动特征和排沙机理,采用欧拉-拉格朗日方法模拟了排沙漏斗水气沙三相流动,其中水相和气相采用雷诺应力模型(RSM)和VOF方法描述,悬移质泥沙用颗粒轨道模型描述。通过对计算的悬移质含沙量垂向分布与实验结果的对比,验证了数学模型的可靠性。计算结果表明:在漏斗室外侧区域含沙量分布整体上较均匀,在漏斗室内侧区域的近底部存在一个明显的高浓度带。作者认为,上述排沙漏斗悬移质泥沙含沙量分布特征主要是由排沙漏斗内的二次流引起的。     

陕南山区中小水库排沙运用

陕南山区中小型水库泥沙淤积问题日益严重，兴利效益降低。通过多年来对陕南商州市南不库和二龙山水库的排沙观测及试验研究表明，利用异重流、浑水水库排泄悬移质泥沙，可以减缓水库淤积，而且排沙耗水少，对以悬移质来沙为主的水库，效果尤为显著，定期泄空冲刷，可以恢复水库已淤库容，使水库保持一定有效库容长期使用，泄空时机一般在汛末或汛初。     

编者的话

《水电站排沙设施》专辑,重点是论述在多沙河流上修建水电站必须设置排沙设施。设计时对如何合理地确定底孔的排沙泄流规模、底孔位置的选择和布置型式及水库运用方式等对电站安全运行的密切关系,必须认真地加以考虑,因为这些问题确定的合理与否,对泄流排沙,延缓坝前淤积速度,减少过机沙量、减轻泥沙对水轮机的磨损及工程的经济效益等均具有特殊重要的意义。     

论进水口前的冲刷地形

在多沙河流上建坝,必须设置排沙孔道,其任务:一是清除坝前淤积泥沙,防止泄洪进水口被淤堵;二是防止或减少泥沙进入机组进水口,以减轻机组的磨损。因此排沙进口必须低于机组进口一定的高程,经常开启冲刷,才能     

水电站的防沙措施

文章通过对水电站水轮机磨损的主要因素进行分析,结合实践经验,总结出泥沙处理措施,在大坝设置排沙底孔、拦沙坎及冲沙槽,防止大量的推移质泥沙大量进入水口闸,大大减少粗沙通过水轮机含沙量。沉沙池降低挟沙水流中泥沙颗粒大于设计沉降粒径的悬移质泥沙、降低水流中含沙量。压力前池是继大坝、沉沙池后的第三道防沙,防止泥沙进入水轮机,造成水轮机的磨损。注重运行时管理水平和及时维修。     

缅甸瑞丽江水电站泥沙模型试验研究

阐述了瑞丽江水电站泥沙模型试验的主要内容和试验方法。通过模型试验研究,肯定了拉沙洞前置的合理性;确定了水库调度的具体方案;并由右岸拉沙底孔的拉沙效果提出加设机组的构想。     

大朝山水电站泄洪消能及排沙建筑物设计

大朝山水电站采用表孔和泄洪排沙底孔联合泄洪的泄洪消能方案。中小流量时，以泄洪排沙底孔、冲沙孔和机组泄流为主；中大流量时，则以表孔、泄洪排沙底孔、冲沙孔和机组联合泄流。表孔采用宽尾墩，台阶式坝面和戽式消力池消能工，泄洪排沙底孔和冲沙孔采用窄缝异型挑流消能。新型台阶式坝面对加快碾压混凝土坝的施工进度、节省工程量和提高工程效益具有积极的意义。     

龚嘴水库库床演变和过坝泥沙

本文通过对龚嘴水库实行汛期按流量级控制运用以来，库床冲淤变化的观测、结合沿程水位资料的分析，说明充分利用入库水、沙变化的有利时机，适当抬高或降低坝前水位，使库床在冲淤变化中实现年内基本平衡，以保持必需的调节库容。减轻库尾回水抬高程度，是合理解决发电与排沙矛盾的有效途径。坝前含沙量具有明显的横向不均匀分布和沿垂线的梯度分布，合理运用底孔是解决“门前清”，减少粗沙过机的重要途径。     

冯家山水库排沙试验模拟研究

冯家山水库是一座位于多沙河流上的大(II)型水库,异重流排沙已较为成功地解决了水库淤积问题。试验通过修建局部坝前水库,观察了异重流在水库模型中的掺混过程及浑水水库的形成过程,并定性地得到了坝前含沙量垂线分布。     

新疆克孜尔水库人工辅助排沙工程排沙效果初步分析

本文通过对2011~2012年克孜尔水库利用人工辅助排沙工程排沙资料进行分析,得出结论:水库"借助人工辅助排沙工程、汛期降低库水位"调水调沙的运用方式,实现了库区黑孜河库段冲淤基本达到平衡,排沙效果十分理想,发挥了水库的综合利用效益。从而为在多沙河流上修建水库如何解决"减少淤积、保持库容、维持冲淤平衡"的问题提供了借鉴。     

Spatio‐temporal variability of suspended sediments in rivers and ecological implications of reservoir flushing operations

High suspended sediment concentrations during reservoir flushing are known to be harmful to biota in downstream river stretches. Therefore, it is common practice to set legal concentration limits for upstream reservoir management operations such as flushings or controlled drawdowns. However, as shown by measurements, there is a considerable spatio‐temporal variability of suspended sediment concentrations both in the longitudinal profile of rivers and in river cross‐sections. To consider this variability in management operations, SED‐FISH—a three‐dimensional modelling approach—was developed to study this variability in a wider context by upscaling cross‐sectional measurements of suspended sediments to high‐resolution three‐dimensional information on the reach scale in an alpine river. The resulting patterns of suspended sediment concentrations were integrated over their respective time of occurrence for various scenarios in order to calculate severity of harmful impacts for target fish species. The modelling results identified refugial habitats with reduced negative impacts in near‐bank zones even for relatively high suspended sediment concentrations in the centre of the river. Moreover, a substantially larger variability of both suspended sediment concentrations and associated harmful impacts was found for a winding riverbed morphology as compared with a straight reach. Both these findings and the developed modelling tool could assist in establishing individual case‐based concentration limits for reservoir management operations in the future and should also be taken into account when planning river regulation or restoration measures.     

燕子崖电站防沙和排沙设施的选择

传统的防沙和排沙工程措施主要有定期冲洗式沉沙池和连续冲洗式沉沙池两种,这些传统技术不能满足高效节能的防沙和排沙要求。通过定期冲洗式沉沙池、连续冲洗式沉沙池、排沙漏斗进行比选,并通过水力计算和对比论证分析。结果表明:排沙漏斗产生稳定的螺旋流,水流流速较大,加速泥沙向中心的排沙底孔和漏斗底部运动;而定期冲洗式沉沙池、连续冲洗式沉沙池中不存在稳定的螺旋流。排沙漏斗具有结构紧凑,工程量和投资最少,泥沙分离率较大,耗水率较少,所以排沙漏斗是一种经济、高效节水的防沙和排沙设施。     

Measurement and quantification of a sedimentation budget for a reservoir with regular flushing

This paper provides a case study of successful removal of reservoir sediment by empty flushing. The main aim of this study was to determine: (i) sediment inflow to the Cachí reservoir; (ii) the pattern and rate of deposition in the reservoir; (iii) the erosion within the reservoir during flushing; and (iv) sediment outflow at a downstream hydrological station during flushing. The results are integrated as a sediment budget for the reservoir. The drainage basin of the Cachí reservoir in Costa Rica is 785 km². The sediment budget for the period between two flushings indicates a sediment inflow to the reservoir of c. 930 000 tonnes and a net accumulation of c. 133 000 tonnes, or 14.3% of the sediment inflow. The sediment throughflow was also c. 133 000 tonnes up to the erosion phase of the flushing, and the outflow during flushing including bed load was 663 000 tonnes, i.e. 71.4% of the sediment inflow. Thus, the flushing of the reservoir was highly effective in releasing sediment. The balance of the sediment budget makes it probable that the major components of the sediment budget are of the right order of magnitude. The main principle to obtain correct sediment loads by the rating‐curve technique was to collect sediment data from a large number of storm events at equal time intervals during rising and falling stages. This was achieved by turbidimeter recordings. Because of the wide scatter of data, sediment rating curves were developed on mean sediment loads in discharge classes to avoid the bias of log regressions. The trap efficiency and sediment throughflow were determined with Sundborg's physically based sedimentation model. The throughflow amounted to 20% of the suspended sediment inflow, which compares well with the empirical budget. The depositional pattern in the Cachí reservoir was surveyed with side‐scan sonar, repeated echo‐soundings, and by excavating pits in deposits when the reservoir was empty. Deposition occurred mainly in the old river channel, indicating that the major part of the sediment is transported by density currents. The volume of eroded material in the reservoir during scour valve release was estimated by echo‐soundings before and after the flushing. Dry bulk density of the reservoir deposits was determined by X‐ray radiographic and densitometric analysis. The radiographic analyses indicated a dry bulk density of 0.4 g cm⁻³ of the loose material in the thalweg, and 0.7 g cm⁻³ of the whole deposition depth on the terraces. Copyright © 2000 John Wiley & Sons, Ltd.     

水库排沙对下游河流鱼类影响研究进展

水库排沙对减轻水库淤积、延长水库寿命和恢复河流泥沙连续性等方面有着重要意义,但是水库进行水力排沙时水库下游河流水体的物理和化学性质的变化可能对鱼类等水生生物产生不利影响,严重时出现死鱼现象.国内外水库排沙时期下游河道含沙量及其颗粒级配、溶解氧浓度、污染物等水质变化对鱼类影响研究表明,微颗粒泥沙淤堵鱼鳃影响其摄入氧气功能和水体溶解氧下降是影响鱼类的两个主要因素,且含沙量及其持续时间、颗粒级配等对鱼类影响机理不同.最后展望了我国今后水库排沙对下游河流鱼类研究内容.