再分析卡里巴拱坝下游河床冲刷严重的原因

 卡里巴(Kariba)拱坝下游河床冲深达57～80 m,是世界上河床冲刷最为严重的拱坝,有着其地质、泄水布置等方面的原因。其中主要原因是泄水中孔出口佛劳德数较低,6股水舌入水后能量聚集,同时河床又未采取保护措施。总结其经验可避免类似冲刷在我国出现,对小湾、溪落渡等高拱坝护坡不护底水垫塘的论证有着重要意义,对其它工程也有参考意义。     

高坝挑射水流对岩石河床冲刷的研究综述

高拱坝大流量坝身泄洪几乎全部采用挑流消能方式，为此分析了国内外关于挑射水流对岩石河床冲刷的各种理论，并对高拱坝挑流消能冲坑深度预测、基岩冲刷的模拟方法、岩石冲刷破坏机理研究等问题进行了综述。同时提出岩石河床冲刷研究的关键课题。     

挑射水流对岩石河床冲刷的研究进展

高坝大流量坝身泄洪几乎全部采用挑流消能方式,分析了国内外关于挑射水流对岩石河床冲刷的各种理论,并对高拱坝挑流消能冲坑深度预测、基岩冲刷的模拟方法、岩石冲刷破坏机理研究等问题进行了综述.同时提出岩石河床冲刷研究的关键课题.     

拱坝溢流水舌对河床作用力及其影响的研究

一、前言 拱坝下游消能采用跌塘式消能工是简便、经济的方法。但是,由于对跌落在坝脚附近的水舌,其巨大能量能否造成河床严重冲刷、护坦损坏以及作用在跌落处附近动水压力的脉动能否引起坝基及坝体振动等方面的评价,却常有不同看法。主要原因是对跌落水舌冲击河床的作用,从理论和实践上还有许多解释不清楚的问题。然而,从水动力学     

顺河向、高倾角大断裂带的拱坝地基综合处理

该文介绍福建省某水电站拱坝地基中河床顺河向、高倾角、大断裂带对拱坝建设的坝基渗漏、压缩变形和岸坡稳定、泄流冲刷的影响及采取的综合处理措施,并初步总结施工中的经验教训,供相似工程参考。     

谈河床的允许冲击动水压力

拱坝坝身及泄水挑流工程在泄洪时，射流落入下游并冲击河床，在河床面上产生动水压力。在工程水力设计中，河床面上动水压力的大小及其承载能力，是设计者十分关心的问题。本文通过原型挑流冲刷资料的分析，对河床允许冲击动水压力进行了探讨。     

关于过水拱坝溢流形式的探讨

一、过水拱坝的水流特性及主要类型就水流情况而言,拱坝过水主要的问题是溢流水舌对下游河床的冲刷和消能问题。从结构条件看,拱坝的稳定主要是靠周缘基岩的支撑,只要下游冲刷不影响到支承拱体的基岩受力范围以内,即不致影响到坝体的安全。另外,坝区地质常常会有顺河节理存在,河岸如受冲刷,会引起岸坡滑方,影响到坝肩支承基岩的稳定。因而有时为两岸地质条件所限,坝顶的溢流长度常受到一定限制。     

南津渡水库闸坝下游河床冲刷问题的试验研究

通过物理模型试验,利用NDV对泄水闸下泄水流右侧区域的三维流速进行测量,重点分析尾坎下游主泄流区和回流区的的水流特性,研究水流对河床的影响,分析南津渡水库闸坝下游河床冲刷破坏的原因。试验研究表明,造成南津渡水库下游回流区河床冲刷的主要原因是流速的分布特点,而造成主泄流区河床冲刷的主要原因是下泄水流所携带的紊动能。     

玄庙观水库拱坝整体水工模型试验研究

玄庙观枢纽工程为双曲拱坝,其特点为窄河床、陡边坡、坝顶溢洪道较宽,泄流时易造成对岸边的冲刷。主要论述在综合考虑闸前流态、水舌挑距及坝下冲刷情况前提下的合理闸门运用方式,根据下游冲刷效果提出对闸墩及消能工进行修改的建议,为类似工程设计提供参考。提出的宣泄不同标准洪水的闸门运用方式,可供管理运行单位参考。     

岩石基础高水头泄水建筑物下游河床的变形

在设计高水头泄水建筑物时,综合实测资料对设计高水头泄水建筑物具有重要的意义。本文研究影响下游河床和河岸变形的水工建筑物的参数。图1示出计算图式;表I就两类水利枢纽——一类下游宽阔,一类位于窄小狭谷中(拱坝)——列出某些几何参数、水力学参数和冲刷坑参数(最大深度冲刷坑的资料较为完整)。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.