碾压混凝土层面抗剪(断)特性尺寸效应研究

碾压混凝土呈层状结构,大约30cm厚为一层,大量的层面成为薄弱环节,层面抗剪强度参数为碾压混凝土重力坝抗滑稳定分析的重要依据。碾压混凝土层面原位抗剪试验是提供层面抗剪参数的主要试验方法。这种试验的试件大、投资多、工作量大,又是大型工程中必不可少的试验项目。结合龙滩碾压混凝土特性试验,研究试件大小对抗剪参数的影响,确定了原位抗剪试验试件的尺寸效应系数,并提出了一个表达式,从而可用小试件代替大试件研究抗剪参数。这将有较高的理论价值和实用价值。     

提高碾压混凝土重力坝层面,抗滑稳定性的措施

近年来，碾压混凝土重力坝沿坝体碾压混凝土层面的抗滑稳定性受到普遍关注．从结构方面考虑，提高碾压混凝土层面的抗滑稳定性可采用使层面向上游倾斜与折斜或局部提高下游坝面附近碾压混凝土层面的抗剪能力等措施．通过对龙滩碾压混凝土重力坝层面抗滑稳定性的分析可以看出：碾压混凝土层面向上游倾斜、折斜，或局部提高下游坝面附近的抗剪强度等措施，可在不增加或很少增加工程量的情况下，大幅度提高其抗滑稳定性，给工程带来较明显的经济效益．     

龙滩碾压混凝土性能研究

本文综合介绍龙滩碾压混凝土试验研究成果．包括４种标号碾压混凝土的强度特性、热学性能、变形性能和耐久性，并与相应的常态混凝土试验成果进行了对比分析，探讨了碾压混凝土的优缺点．从材料方面论证了建造２００ｍ龙滩碾压混凝土重力坝的可行性     

碾压混凝土坝信息

据统计资料，截止１９９８年底，２８个国家已建和在建的ＲＣＣ坝超过１５ｍ的共２０９座，其中以中国（４０座），日本（３６座）为最多，美国（２９座）次之，欧洲以西班牙（２１座）为最多。ＲＣＣ坝超过１００ｍ的有１９座，其中日本１１座，中国８座。全世界ＲＣＣ重力拱坝共５座，其中中国２座，南非３座。全世界ＲＣＣ拱坝共４座全部在中国。在碾压混凝土拱坝技术中，我国有创新。本世纪我国将开始兴建龙滩特高碾压混凝土重力坝，坝高２１６５ｍ（一期工程１９２ｍ）中国ＲＣＣ特点是：高掺优质粉煤灰，通常为二级配混凝土；薄层（…     

龙滩碾压混凝土重力坝温度应力研究

结合龙滩碾压混凝土重力坝的工程实际情况，采用广义约束矩阵法研究了该坝典型坝段的温度应力分布及温控安全系数问题，给出坝段的最高应力区分布及自重、水压力对温控的影响规律等重要结论，为龙滩碾压混凝土重力坝的设计和施工提供了参考依据。     

碾压混凝土重力高坝设计中的若干关键因素（Ⅰ）

碾压混凝土重力高坝设计中的若干关键因素（Ⅰ）［美国］Ｇ．Ｓ萨卡里等主题词碾压砼坝，重力坝，高坝，坝设计，因素，施工方法，试验研究目前。根据已建ＲＣＣ重力坝的施工经验和资料，正在设计几座坝高超过１２０ｍ，体积超过１００万ｍ３的大型碾压混凝土重力坝（简称...     

龙滩碾压混凝土室内外抗剪试验结果对比分析

对龙滩大坝碾压混凝土的室内抗剪、现场原位抗剪试验和芯样抗剪试验结果进行了对比分析。室内和现场抗剪试验结果表明,随着层面间歇时间的延长,3种强度等级的碾压混凝土的抗剪强度均下降,尤其是冷缝出现后抗剪强度最低。采用小值平均法和保证率为80%时统计法分析,3种强度等级的碾压混凝土现场原位抗剪试验的f′、c′值均能满足设计要求,小值法较统计法的f′值稍高,c′值稍低;分别用小值法和统计法得出的f′、c′值计算出的抗剪强度差别不大,小值法稍低。除去尺寸效应和龄期的影响后,两种强度等级的芯样抗剪强度均大于设计抗剪强度。     

多轴应力条件下碾压混凝土层面抗剪强度试验研究

针对碾压混凝土重力坝和拱坝等坝体真实的工作受力状况，对碾压混凝土拱坝所用二级配混凝土材料成型的本体、分层处理和分层不处理试件，进行了单轴及多轴应力条件下的剪切试验研究。试件尺寸为150mm×150mm×150mm，试验比较了不同应力状态对本体和含层面试件的抗剪强度和变形特性的影响，结果表明，在低应力压剪和压压剪应力状态下，所有试件抗剪强度和极限变形都有所提高，在有拉应力存在的状态下，所有试件抗剪强度有所降低，复合应力状态下三种试件强度和变形特性有一定的差异。在以上试验基础上给出了碾压混凝土在复杂应力状态下的多轴剪切强度破坏准则。     

龙滩碾压混凝土坝渗流与应力场耦合分析

结合龙滩碾压混凝土重力坝的渗透特性，考虑碾压混凝土层面 流及其力学效应以及坝体应力状态对层面渗透性的影响，采用碾压混凝土坝渗流场与应力场耦合分析的数学模型及其有限元数值解法，对龙滩碾压混凝土重力坝进行了渗流场与应力场耦合分析，为工程设计提供了参考依据。     

龙滩碾压混凝土重力坝地震影响分析

结合龙滩碾压混凝土重力坝，采用频率响应分析方法对高碾压混凝土重力坝的地震响应规律进行了较为深入的探讨，分析了不同频率地震动对龙滩重力坝坝体动力响应的影响规律，所获结论对重力坝抗震设计及抗震研究工作提供了依据。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

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。     

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.     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

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。     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.     

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。