Hardfill材料作垫层的面板堆石坝动力分析

面板堆石坝在强震作用下,面板竖缝和周边缝可能产生较大的张拉和剪切变形而导致发生渗漏。Hardfill的材料性质介于混凝土和碾压堆石体之间,用Hardfill材料作垫层能够有效减小混凝土面板及竖缝和周边缝的地震变形。经过三维有限元动力分析,计算结果表明应用Hardfill材料做垫层能够显著减小面板的地震反应和面板接缝的地震变形。     

建在堆石体上的面板堆石坝趾板应力变形分析

对于混凝土面板堆石坝，趾板能否置于堆石体或砂砾石覆盖层上，以减少开挖工程量，是目前人们较为关心的研究课题之一。对泰安抽水蓄能电站上池的混凝土面板堆石坝进行的 三维非线性有限元计算，研究分析河床坝段趾板建在堆石体上的对面板应力、变形以及周边缝位移的影响，结果表明，这些应力和位移与趾板建在岩基上的一般面板堆石坝有些不同的变化规律，但尚未超出一些已建工程相应的实测值。     

胶结砂砾石在大石峡面板坝增模区设计中的应用

大石峡水利枢纽工程坝址区地形地质条件复杂,河谷狭窄,两岸陡峻,坝前发育规模较大的变形体,河床布置35 m高的高趾墩以避免河床趾板槽开挖对变形体稳定性的影响。河床面板搭在高趾墩顶部,必然在河床面板底部形成堆石体厚度向上和向下喇叭形渐变,该处堆石体的变形梯度如不受控制将直接影响河床面板底部的应力变形和周边缝接缝变形,设计在高趾墩下游和两岸陡峻岸坡设置了胶结砂砾料增模分区;经三维有限元静力计算分析,对河床面板的应力变形和周边缝接缝变形改善效果明显,此项措施可在高面板坝变形控制方案中推广应用。     

基于参数反演法面板堆石坝长期运行变形分析

根据水布垭面板堆石坝坝体几何参数和周围山体地形地质资料,建立面板堆石坝三维数值计算模型。以坝体在竣工时的变形实测资料为依据,采用智能位移反演方法反演获得堆石体流变变形参数,对坝体的长期运行变形进行计算分析。通过对大坝堆石体及面板在运行期的应力应变分析成果,可以看出大坝在竣工蓄水后经过一段时间的运行,坝体的整体发生了一定的沉降变形,面板垂直缝、周边缝及止水部位也相应出现了一定变形。通过与实测比较分析,坝体变形在合理范围以内并趋于稳定。在今后坝体的长期运行中,要对出现变形位置的测点加强监测,确保整个坝体长期安全稳定运行。     

基于子模型法的面板堆石坝三维应力变形分析

基于三维有限元非线性方法,考虑某高面板堆石坝面板分期施工浇筑的特点,建立精细模拟面板特性的子模型,用有厚度的接触面单元模拟坝体与面板的接触面,设置相应的连接单元模拟面板缝的相互作用,分析了该面板堆石坝在施工期和蓄水期坝体和面板的应力变形,并与类似坝高的面板堆石坝的计算或监测结果进行比较。结果表明:在施工期和蓄水期坝体的最大沉降值约为坝高的1%,位于次堆石区;面板应力以压应力为主,拉应力主要集中在面板与周边山体连接处;周边缝的最大错动剪切变形、最大张拉变形及最大沉降剪切变形均未超过30 mm。     

复杂地形对面板坝面板应力和变形的影响分析

某混凝土面板堆石坝坝高144m．河谷地形复杂。采用三维非线性有限元法,建立了坝体和坝基的三维有限元模型．模拟了大坝填筑施工过程和水库蓄水过程．分析了运行期面板的应力变形及周边缝的变位特性,研究了复杂地形条件对该坝面板应力和变形的影响。计算表明：该混凝土面板堆石坝的面板应力受地形的影响较大,与坝体断面几何形态密切相关。左岸次堆石区变形大．面板应力较大,而右岸岩体的支撑作用显著,面板应力较小。右岸陡坡处及左右岸变坡处周边缝的变形较大。     

主、次堆石区分界对面板坝应力变形影响研究

为了更好地研究面板堆石坝主、次堆石区分界线位置对坝体、面板的应力及位移的影响,结合水布垭面板堆石坝的设计资料,通过拟定主、次堆石区分界线分别位于坝轴线上游、下游及坝轴线3种方案,在竣工期(坝体施工完毕)和蓄水期(水库蓄水到正常水位)不同工况条件下,利用ANSYS的二次开发功能进行三维非线性应力应变分析计算,得到了3种方案的坝体应力、面板应力、坝体位移、面板位移及面板垂直缝、周边缝三向位移成果,通过对3种方案的计算成果进行比较分析,确定了主、次堆石区分界线位于坝轴线下游较为合理。     

公伯峡面板堆石坝堆石流变特性反演分析

为了分析堆石流变特性及其对公伯峡混凝土面板应力变形的影响,利用原位观测资料对公伯峡面板堆石坝的变形性态进行分析,采用Merchant黏弹性流变模型,反演计算得到相应的流变参数,并用反演得到的流变参数对大坝受力变形进行计算分析。结果表明:堆石的流变作用较明显,流变期间沉降计算值与实测值的变化规律较吻合,堆石流变对面板应力变形、垂直缝和周边缝变形有较大影响;所采用的流变模型和反演得到的流变参数较合理,能够预测面板坝轴向应力和裂缝的发展趋势。     

高混凝土面板堆石坝堆石体施工期变形研究

1引言随着高混凝土面板堆石坝的建造,特别是200m级高坝的变形和应力与一般大坝相比,变化巨大。在已建的一些大坝中发生了堆石体变形较大,混凝土面板裂缝偏多、局部挤压破损,周边缝位移值高等现象,国外工程也有类似的报导。这些经验和教训,给设计、施工、科研等提出了更高的要求     

狭窄河谷中混凝土面板坝的应力变形规律及工程措施研究

为深入了解河谷地形因素对混凝土面板堆石坝应力变形特性的影响,采用一个典型的混凝土面板堆石坝三维有限元模型进行了不同岸坡坡度与河床宽度等影响因子的分析研究,并在总结已有相关研究成果的基础上,结合工程实例,探讨了改善峡谷地区混凝土面板堆石坝应力变形特性的工程措施。研究成果表明：河谷地形对大坝的作用主要表现在岸坡对坝体和面板的约束及顶托作用,这种作用随大坝长高比的增加而减弱。对于修建于狭窄河谷中的面板坝,其堆石体位移梯度和面板的压应力数值相对较大。工程上可采取提高堆石体压实密度,设置岸坡增模堆石区,以及合理确定面板浇筑时机和设置可吸收变形的面板纵缝填充材料等措施,以控制坝体变形并改善面板的应力状态。     

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。