某堆石坝面板混凝土推荐配合比试验研究

混凝土推荐配合比是面板堆石坝建设实践中,混凝土浇筑所依据的最重要技术参数之一。面板混凝土原材料的强度、性状及成分等都会影响混凝土的性能,原材料的工作性能直接影响到混凝土拌合物的工作性能。为此,选取某面板堆石坝的面板混凝土推荐配合比展开试验研究。结果表明,从混凝土原材料的研究入手,选用满足工程及规范要求,经济实惠的原材料进行混凝土配合比试拌、再进行混凝土性能研究,选定最优的混凝土配合比。再经大坝面板各方案混凝土配合比复核试验及相应的性能复核试验,最终确定满足设计要求的面板混凝土施工推荐配合比。这一试验研究方法及成果可供类似水利工程借鉴参考。     

姚河坝水电站混凝土试验研究

针对南桠河姚坝水电站混凝土工程原材料及混凝土配合比和性质，进行了较为全面的试验研究。试验结果表明混凝土工程所使用的原材料及配合比能满足该工程要求，同时结合其原材料特性及工程使用环境，建议在混凝土工程中掺用一定比例的Ⅱ级粉煤灰。     

月潭水库坝体混凝土配合比设计

为满足月潭水库建设水泥用量少、混凝土水化热低、耐久性能好的设计技术要求,通过对混凝土用原材料试验检测,选出优质、经济的原材料,并进行大量配合比试验、混凝土拌合物性能试验及混凝土力学、耐久性能试验以及热学性能试验,最终达到满意效果。     

水工抗冲磨混凝土原材料选用分析

文中介绍了水工混凝土的冲磨破坏机理及研究现状,结合张峰水库抗冲磨混凝土配合比试验对抗冲磨混凝土的原材料选用进行分析,通过原材料优选研制出了经济合理满足设计要求的抗冲磨混凝土。     

平班水电站左岸重力坝常态混凝土配合比优化设计

根据平班水电站所采用原材料的特性,经过混凝土配合比优化设计试验,应用混凝土"双掺"技术及粉煤灰"超代"技术,揭示了各原材料相互间的组合及变化规律,改善和提高混凝土的技术性能,达到保证满足工程技术要求以及经济、节约目的.     

紫坪铺大坝面板混凝土试验研究

通过对紫坪辅水库大坝面板混凝土原材料、外加剂品种以及混凝土配合比设计试验研究，得出了既满足设计要求，又满足强度、抗渗及耐久性要求的面板混凝土配合比。     

呼蓄电站上水库防渗面板沥青混凝土试验研究

针对呼和浩特抽水蓄能电站上水库库区位于严寒地区,防渗层沥青混凝土抗冻断温度要求达到-45℃,在室内对沥青混凝土矿料、沥青原材料及沥青混凝土的配合比进行了试验研究,同时在现场对沥青混凝土的摊铺施工工艺进行了试验。试验结果满足工程设计要求,用于该工程实际,效果良好。     

小湾拱坝混凝土材料及温控研究

小湾拱坝最大坝高292m,混凝土通仓浇筑最大块长88m,混凝土原材料及温控设计是高拱坝关键技术之一。以科研及试验为基础,确定了“高强度、高极限拉伸值、中等弹性模量、低热、不收缩”的混凝土设计原则;以混凝土性能指标作为选择原材料的最终判据,提出了较优的混凝土配合比及原材料技术指标;采用ANSYS通用软件上二次开发的计算程序进行温度场及温度应力的仿真计算,提出温差标准、温控措施和要求,并得以实施和验证。     

高原高寒地区泵送C20混凝土试配实践的分析与探讨

原材料是决定混凝土性能的主要因素,材料的变化将导致混凝土性能的波动。为满足混凝土设计强度、抗冻性、抗渗性等要求和施工和易性的需要,混凝土施工配合比必须进行优选试验。详细介绍了吉沙水电站混凝土配合比设计的原则、原材料的检测、外加剂的选用及混凝土配制强度等,可供以后混凝土配合比设计参考。     

大桥水库面板混凝土试验研究

通过对大桥水库面板混凝土原材料、外加剂品种的选取，前期混凝土配合比，施工配合比试验研究，得出了既满足施工要求又满足强度，抗渗及耐久性要求的最优面板混凝土配合比。     

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。     

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.     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。