三峡工程左导墙碾压混凝土施工

为了优化施工，进而为三峡工程三期临时挡水围堰的碾压混凝土施工模索经验，左导墙结构按碾压混凝土设计。通过施工实践认为：碾压混凝土的总胶材用量不低于160/^3,而粉煤灰掺量可大于50％；Vc值在机口为4－7s、仓面为5－10s；开碾时间控制在0.5h左右，2h内完成各条带的碾压工作；做好碾压施工的入仓方案；提前做好快速上升模板的研究工作。     

彭水大坝碾压混凝土现场试验研究

碾压混凝土的不同施工工艺、不同间歇时间、不同层面处理措施对碾压混凝土层面抗剪性能的影响较大.彭水水电站主体工程碾压混凝土浇筑之前,进行了较全面的生产性试验,提出了适合彭水水电站工程实际的碾压混凝土施工工艺和层面结合质量控制标准:碾压混凝土拌和物的Vc值平均6.1s,拌和物的亲和性和工作性较好,仓面泌水较少;二级配碾压混凝土拌和物的含气量平均为3.1%,在实际施工中含气量应提高到3.5%以上,以满足抗冻等级F150的要求;最佳碾压遍数为无振2遍+有振8～10遍,碾压层厚以采用35cm为宜.     

某水利工程二道坝石粉砂碾压混凝土基本性能研究

碾压混凝土浇筑坝体过程中,由于水化热作用易形成温度裂缝.结合某水利工程坝体施工过程中出现混凝土表面裂缝等质量问题,文章研究矿物掺合料取代率,用以改善碾压混凝土的施工性能.研究结果表明当微珠掺量为20％,混凝土VC值为2.3 s,碾压后混凝土浆体量饱满,可充分压实,提升硬化混凝土性能;当矿渣掺量达到30％,混凝土28 d抗压强度最优,矿渣对于中后期强度贡献较多.     

构皮滩水电站下游围堰RCC施工工艺试验

构皮滩水电站下游围堰采用内部为碾压混凝土,外部为常态混凝土的形式进行施工,为了能够得到一个合理的施工参数,在施工前需要进行碾压混凝土工艺试验以确定碾压遍数、铺筑厚度、层间处理、变态混凝土加浆量等参数.介绍了构皮滩水电站下游围堰碾压混凝土工艺试验的过程与结果,该试验成果已成功应用到了施工生产当中,为构皮滩水电站下游RCC围堰优质高效的施工打下了坚实的基础.     

混凝土面板砂砾石坝现场碾压试验和大型相对密度试验研究

本文首先对卡拉贝利工程中混凝土面板砂砾石坝筑坝材料进行了现场碾压试验,在选定施工机械(SR22MP自行式振动碾)和振动参数(激振频率28～32Hz,行进速度2.63～8.6km/h)后,研究了铺料厚度、碾压遍数、加水量等因素对碾压干密度的影响规律,并根据试验结果确定了大坝碾压施工控制参数。然后采用振动台法,对不同含砾量的筑坝砂砾料进行了大型相对密度试验,确定了不同相对密度下的含砾量P5与干密度Pd的关系曲线,为确定设计参数和碾压施工控制提供了坚实的科学依据。这些成果不但直接为卡拉贝利工程混凝土面板砂砾石坝的设计和施工提供了科学支撑,对其他类似工程也有重要参考价值。     

碾压混凝土抗拉性能及绝热温升试验研究

１引言碾压混凝土施工方法是把低水泥用量、干硬性的混凝土用振动碾一层一层地压实，采用土石坝的施工方法浇筑混凝土材料，以达到加速施工、减少工程造价的目的碾压混凝土的主要特点是水泥用量低（５０～２５０ｋｇ／ｍ３），掺合料用量高（２５％～８０％），拌和物呈干硬性，适合大体积混凝土的浇筑２试验结果２１原材料情况和碾压混凝土及拌和物的一些性能试验用材料：普通硅酸盐５２５号水泥、Ⅰ级粉煤灰、天然砂（细度模数为２６５）、花岗岩人工碎石（粒径为５～８０ｍｍ）、木钙减水剂碾压混凝土配合比及拌和物性能如表１所列，碾压…     

乌东德水电站二道坝工程圆满完成低热水泥碾压混凝土试验

<正>2017年11月2日,在乌东德水电站主体工程最后一个开挖项目——二道坝工程项目即将全面完成之际,为提前做好二道坝施工技术储备,结合混凝土碾压各施工环节,乌东德水电站二道坝工程正式开启低热水泥碾压混凝土试验。本次试验,是为测试碾压混凝土层面处理工艺,取得最佳摊铺、碾压配套设备的工艺参数,以及验证适应低热水泥碾压混凝     

采用新技术修建普定水电站第一期碾压混凝土节资88万余元

国家“八五”科技攻关项目——装机三台、总容量7.5万kW、年平均发电量3.4亿kw·h的贵州普定水电站,坝体采用高掺粉煤灰干硬性混凝土、整体通仓薄层浇筑、全断面碾压连续上升的新技术施工,今年汛期前碾压完毕的3.6287万m~(?)混凝土,节省工程资金88.44万元。兴建普定水电站引人注目的最大特点,是我国首次采用碾压混凝土筑坝技术施工高拱坝,与传统的常态混凝土筑坝方法相比,具有水泥用量少(每立方碾压混凝土少用水泥161.7kg)、施工速度快、工程造     

浅谈苏阿皮蒂水利枢纽碾压混凝土施工过程中的质量控制

为了保证大坝碾压混凝土的施工质量,除了做好原材料、配合比及拌和物的质量控制外,还要做好现场施工过程的质量控制。阐述了几内亚苏阿皮蒂水利枢纽在施工过程中对碾压混凝土的层间结合面处理、混凝土运输、入仓温度、入仓卸料、摊铺、碾压、变态混凝土振捣及灰浆、养护等工序的质量控制措施,这些质量控制措施保证了碾压混凝土的施工质量和工程的整体施工进度,工程建设得以顺利开展。     

变态混凝土

<正>变态混凝土是指在碾压混凝土拌和物中加入适量的水泥灰浆(一般为变态混凝土总量的4%~7%之间),使其具有可振性,再用插入式振捣器振动密实,形成一种具有常规混凝土特征的混凝土。在水利水电施工中,时常用到碾压混凝土,它是低水灰比,坍落度为零的水泥混凝土,具有施工快、强度高、缩缝少、水泥用量少、造价低、减少施工环境污染等优点,经振动压路机振动、碾压成型,不论是大型工程,还是局部改扩建工程,施工方便快捷。但是在施工中,有些部位没法用机械设备碾压,这些部位的混凝土密实度是一个问题,     

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。     

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.     

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。