溢洪道消能方式的选择探讨

以新疆克孜河水库枢纽为背景,结合物理模型试验,对其溢洪道建筑物传统底流消能和跌坎型底流消能方式的水力特性展开比较分析,并进行了跌坎型底流消能工冲击区时均压强经验公式的推求,对入射角、入池能量、跌坎深度等因素变化下跌坎型底流消能工淹没射流区主流轴向时均速度衰减规律进行总结,可作为跌坎型底流消能方式应用的参考。     

跌坎型底流消能工水力特性的试验研究

采用水力学试验方法,对跌坎型底流消能工的水流流态、时均动水压力分布以及临底流速进行了分析。并对影响消力池水力特性的跌坎深度和水流入池角度进行了研究。研究表明跌坎型底流消能工能有效解决高水头、大单宽流量消力池水力学指标过高的问题。     

跌坎型底流消能工淹没射流区流速衰变规律

跌坎型底流消能工消力池内的流态为淹没射流和淹没水跃的混合流态,为了解淹没射流区的水力特性,应用紊动射流理论,分析了淹没射流区主流的扩散规律、主流轴向最大时均速度的衰变规律。采用水力学试验方法,借鉴目前研究成果的基础上,开展了淹没射流区主流轴向最大时均速度衰变规律的研究。通过试验研究结果,推导出以入池角度为控制目标的跌坎型底流消能工淹没射流区主流轴向最大时均速度衰变的半经验公式。     

跌坎型底流消能工冲击区时均动水压强分布 与抗冲磨强度确定

在跌坎型底流消能工消力池内水流流态分区的基础上,根据自由紊动射流理论,得出不同入射角度下冲击区时均动水压强半经验公式。利用冲击区底板时均动水压强分布图,在角度和流量不变的工况下,跌坎的变化对底板时均动水压强的影响,以及角度跌坎不变的工况下,流量的变化对底板时均动水压强的影响,显示出冲击区最易遭受冲磨与破坏的区域。以某水库工程为例,由实测数据推求经验公式相关参数,验证经验公式的可行性,进一步结合临底流速求出消力池底板混凝土抗冲磨强度分布图,对底板分区,为合理确定消力池底板混凝土强度等级提供参考。     

跌坎型底流消能试验研究

为了减小高坝泄洪雾化的影响,对比传统底流消能工,进行了水工模型试验。通过试验,对跌坎型底流消能工的水流流态、临底流速以及脉动压力分布进行了研究分析,结果表明：跌坎型底流消能工可大大降低临底流速,减小消力池底板上的脉动压强,消能效果较好;同时还可抬高消力池底板高程,缩短消力池长度,节省较多的工程量,经济效益明显。     

跌坎型底流消能工的跌坎最小深度研究

跌坎型底流消能工消力池内的水力特性受到跌坎深度的影响。应用平面紊动射流理论,以消力池内允许的最大时均动水压强为控制目标,对于跌坎最小深度的确定方法进行了初步分析,建立了计算跌坎最小深度值的理论公式。通过水力学试验方法,得到消力池底板时均动水压强与跌坎最小深度之间的关系,同时与跌坎最小深度试验值进行了比对,对本文建立的理论公式进行了验证。     

不同跌扩组合对扩散式泄槽底流消能水力特性影响研究

通过水工模型试验,研究跌扩型底流消能工进口接扩散角为3°的扩散式泄槽,在不同跌坎深度、不同边墙突扩宽度的组合下,其消能工内临底流速、时均压强、脉动压强方差值以及尾水渠水流流态的变化情况。结果表明:当跌坎深度由0.05 m增加到0.10 m,边墙突扩宽度由0.30 m增加到0.35 m时,消力池内临底流速降低、时均压强逐渐回升,尾水渠水流较为平顺。进一步增大跌坎深度和边墙突扩宽度,消力池内水力特性和出口水流流态虽继续改善,但效果已不明显。     

跌坎型底流消能流态转捩及控制研究

跌坎型底流消能工是一种建立在常规底流消能工基础上的新型消能工。通过理论分析得出,跌坎型底流消能工消能率随着跌坎高度与上下游水深的变化而发生变化,且不同入池Fr下,满足消能率所需坎高与水深不同。结合某大型水电工程进行验证,针对上游相对水位120.0~140.0 m、下游相对水位40.0~50.0 m,跌坎型消力池内水流流态特征进行分析。研究结果表明,跌坎型消力池内水位波动最大值发生在跌坎下游50~100 m范围内;随着跌坎型消力池跌坎高度的变化,消力池内水流可呈现出三种不同流态特征;当跌坎断面采用收缩体型后,跌坎高度可得到提升,有效地保障消力池内水流流态稳定和消能效率,改善消力池内临底水力学指标。     

跌坎型消能工冲击区流速衰减规律研究

跌坎型底流消能工冲击区对消力池的消能效率具有决定性的影响,而冲击区入射主流轴线流速沿程衰减规律及机理尚不明确。采用水工模型试验方法,开展了冲击区主流轴线最大流速与跌坎深度、入池流量之间相互关系的研究,结果表明,跌坎型底流消能工冲击区入射主流轴线流速的衰减遵循一般的射流衰减规律。通过水工模型试验结果的无量纲化,给出了u_((i)max)/u_0(入射主流轴线各特征断面点流速的无量纲值)—x_i/L(入射主流轴线各特征断面点距离的无量纲值)的关系,研究结果表明:跌坎型底流消能工冲击区入射主流轴线流速衰减规律不受跌坎深度、入池流量的影响,具有相似的衰减趋势;入射主流轴线流速沿程衰减拟合曲线表明入射主流轴线流速沿程得到充分衰减。     

入池角度对跌坎型底流消能工水力特性影响的数值模拟

跌坎型底流消能工是在常规底流消能工基础上发展起来的一种新型消能工.就入池角度对跌坎型底流消能工水力特性的影响进行数值模拟,并将模拟结果与试验数据对比分析.二者基本吻合.表明数值模拟方法有效可行.同时,研究发现入池角度对跌坎型底流消能工水力特性影响较大,选择合适的入池角度以提高消能效率是确定该型消能工体形的关键之一.     

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.