多沙河流引水渠渠首闸引水能力改善方法初探

针对多沙河流河床冲淤调整幅度大,冲淤交替发生,特别是一些大型水库的建成运用,不同程度地改变了原有河床的冲淤演变规律,直接影响引水渠首取水能力,导致渠首闸乃至整个输水渠系不断改建的现实问题,着重分析三门峡水库和小浪底水库不同运行阶段对河床冲淤的影响,比较有坝式引水和无坝式引水的两种情况及存在的问题,论证了不同渠首闸布置形式对变动河床的适应性;重点介绍了一种适用于多沙河流灌区取水条件经常调整的分层取水方法;概述了分层取水闸的结构设计和运行管理简况,以黄河下游小开河引水闸为例,并与黄河下游已改建的单层渠首闸作比较。结果表明:多层渠首闸能够分层取水,应对不同水沙情况,适应河床调整,保证设计引水流量,延长渠首闸使用寿命,有利于渠首闸闸前闸后引水渠的长期运用,使灌区工程效益得到有效发挥。     

洞子村水电站开发方案比选设计

洞子村水电站工程位于黄河支流湟水下游干流上,是甘肃省湟水河下游河段水电梯级开中规划的第五级电站．工程建成后主要用于发电。在可行性研究设计过程中研究了2种开发方案,即引水式开发方案和河床式开发方案,其中河床式开发方案选定上、下2条坝线进行比较。表2个。     

边界条件对三峡坝下游河床演变影响

河流发育和河床演变受多种因素的影响,其中边界条件是重要的因素之一.根据已有河床组成、地质钻孔成果,阐述了三峡坝下游河道边界条件,总结了三峡坝下游河段河床演变特点,分析不同的边界条件对坝下游河床演变的影响.分析表明,基岩质或硬土石质河岸边界对河床剧烈演变起制约作用;砂-土二元边界河岸抗冲性很差,对河床演变的约束力较弱,主要体现在下荆江;粘性土质河岸对弯道的发展起重要的抑制作用;护岸及河控工程很大程度上抑制了河床横向变形,但易造成河床的纵向较剧烈变化.     

福州市区内河实施引水冲污后若干水文技术问题

福州市区内河引水冲污工程已破土动工,引水对内河河床演变的效应,冲污对闽江水域水质的影响,这两个问题都极为重要,不可忽视,应当列入议程。     

人类活动对汾河下游河床演变的影响

随着经济建设的快速发展，人类为开发利用水资源而兴建了大量水库和引水工程，改变了河流的水沙系列，为防洪和开发滩涂进行的河道整治影响甚至改变了河床的自然演变。人类活动已成为影响河床演变的一个重要因素、我们在改变河床自然演变规律、取得工程效益的同时，也将可能在为工程本身付出相应的代价。为了使河道整治更好地适应河床演变规律，减少河道工程的负作用，本文分析了汾河下游河道整治工程对河床演变的影响，以便为以后的河道整治提供一些参考。１汾河下游河道概况晋中与临汾交界王庄以下至入黄口庙前为汾河下游。按照河型大致分…     

新疆平原区多沙河流演变规律及引水枢纽设计

新疆已建的400多座引水渠首，绝大部分建在河流出山口丘陵区，在平原区细沙河床上修建的引水枢纽较少。由于细沙河床段纵坡缓，河床抗冲能力低，水流力界条件复杂，修建拦河引水枢纽对原河道的冲游特笥影响较大，河道水流对边界条件的改变较为敏感。因此，对平原区多沙河流引水枢纽研究意义重大。作者在分析新疆平原河流河床演变规律的基础上，提出了平原区引水枢设计要点设计方法，并对有关问题进行了探讨。     

山西省垣曲县李家河引水工程引水量分析计算

介绍了西阳河和李家河引水工程的基本情况。通过计算降水量、地表径流以及基流,得到引水工程坝址上游的来水量,并对来水量进行了月分配,扣除下游生态用水、蒸发渗漏损失水量后,得到不同保证率情况下引水工程的可引水量。通过分析,认为李家河引水工程引水后不会对流域其他用水户的用水造成影响。     

葛洲坝枢纽下游河段河床演变分析

为研究三峡施工期及运用后,葛洲坝枢纽下游河段河床演变及水位变化对航运的影响,根据实测资料,对葛洲坝枢纽下游河段的水沙过程及河床演变、宜昌水位下降的情况进行了分析.认为近坝段经过葛洲坝施工期及正常运行期,河床已处于相对平衡.宜昌枯水位的降低主要是由于泥沙补给减少、人工采挖沙石骨料以及近坝段河床明显冲刷造成的.坝下游枯水航道问题可通过调度和工程措施途径解决.     

嫩江江道演变对引嫩渠首引水的影响及整治措施

分析了嫩江江道演变对引嫩工程引水的影响,提出了修筑顺坝、丁坝、采取固床、延长鱼咀工程及植柳固滩的江道整治的措施,并取得了明显效果.     

毛阿提引水枢纽分水排沙试验研究

为研究毛阿提引水枢纽上下游冲淤演变状况及消能防冲效果,对毛阿提引水枢纽设计方案进行了系列动床试验,试验测定了各典型流量下枢纽上、下游河床、整治段冲淤演变情况,冲淤变化历时、冲淤范围和冲刷深度。结果表明:毛阿提引水枢纽总体布置基本合理,消能防冲效果良好。根据试验结果,给出了实际运行中的各个闸门的运行方式,供运行管理单位调度方参考。更多还原     

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.