水闸大体积混凝土温控与防裂方案研究

水工混凝土裂缝产生的原因,与基础约束情况、混凝土的施工质量、混凝土温度控制水平和伸缩缝设置等有密切的关系,文章针对闸底板大体积混凝土温控与防裂措施进行了阐述,对黑岗口水库闸底板工程采用的常规大体积混凝土温控防裂、预埋冷却水管、设置后浇带、温控监测措施等进行了叙述,这些技术在该工程中温控与防裂效果良好,类似工程值得借鉴。     

后浇带施工技术在泄洪闸闸墩防裂中的应用

结合实际闸墩工程中后浇带结构的设计与施工,应用混凝土温度控制原理,对比混凝土结构设置后浇带前后温度和应力的变化,分析后浇带的防裂效果,表明了在混凝土闸墩中设置后浇带是进行混凝土温度控制和防止裂缝产生的有效方法。     

淮安某立交地涵温控防裂措施仿真分析

为解决立交地涵施工期混凝土的温控防裂问题,用三维温度场和应力场有限元法对淮安某立交地涵工程混凝土结构进行施工期的仿真计算分析,对结构施工分层、设置后浇带、部分整体浇筑和多种保温等混凝土防裂措施进行了计算和比较,了解这些防裂措施的效果,进而找出最有效的防裂措施,为工程混凝土结构的施工提供科学指导.     

超长钢筋混凝土结构无缝施工技术

在超长钢筋混凝土结构施工中,为防止混凝土受温度应力和干缩应力而引起开裂,施工中通常采用设置后浇带的方法加以处理。一般不超40m设一道后浇带,等40天后补浇膨胀混凝土。这种常规的施工方法,工序复杂,施工时间长,质量不易保证。如在施工中,利用UEA膨胀混凝土补偿收缩的原理,采用膨胀加强带代替后浇带,可实现超长钢筋混凝土结构的无缝施工。潍坊市孵化器大厦工程位于潍坊市高新区,框架剪力墙1.工程概况     

船闸闸室墙开裂机理及防裂方法研究

船闸闸室墙在中间浮式系船柱附近的混凝土易产生裂缝,影响船闸工程整体稳定性。通过对闸室混凝土的温度应力展开仿真分析和实际船闸工程混凝土裂缝调研,发现整浇闸墙中间系船柱附近和上下游侧墙中间下部混凝土在施工期易产生竖向裂缝。因此,考虑闸墙中部采用后浇带的方式,并且比较了后浇带不同施工方案,发现采用后浇带能降低闸室上下游侧墙混凝土的最大主应力,防止裂缝的产生;但仅采用后浇带的方式,会导致中间浮式系船柱附近的后浇混凝土开裂风险增加;因此,可通过改变后浇带浇筑顺序和采用微膨胀混凝土的方式,提高中间浮式系船柱附近混凝土的抗裂能力。     

自流平混凝土在盐河闸除险加固工程中的应用

盐河闸闸身加固空间狭小、钢筋密集,新浇混凝土为"∏"形薄壁结构,施工难度较大。钢筋、模板安装后整个浇注区是封闭的,其结构特点决定了施工人员无法进入仓面浇筑振实混凝土,传统施工方法与普通混凝土不能满足质量要求。通过对常规浇筑混凝土、自流平微膨胀混凝土、喷射混凝土等三种施工方案进行技术比较,采用自流平微膨胀混凝土方案能够满足混凝土密实性和表面平整度的要求。介绍了盐河闸闸室洞身自流平混凝土施工技术要点,提出了自流平混凝土施工经验和建议。     

水工隧洞衬砌混凝土温控施工技术进步与防裂效果分析——评《水工隧洞衬砌混凝土温控防裂技术创新与实践》

正近年来,随着衬砌混凝土技术的不断发展,基于温度变化导致的混凝土裂缝现象得到了一定程度的控制,相比较其它类型混凝土施工项目来说,水工隧洞衬砌混凝土温控施工技术难度大、工艺复杂,在实际项目实施过程中防裂效果并不稳定。《水工隧洞衬砌混凝土温控防裂技术创新与实践》(樊启祥、殷亚辉,中国水利水电出版社 2015版)以水工隧洞衬砌混凝土温控防裂技术为主要研究对象,全书共分为十章,第一、二、三张分别就水工隧洞衬砌混凝土裂缝现象、衬砌混凝土近代技术、温     

氧化镁微膨胀混凝土的变形特性研究

本文通过长达十余年的自生体积变形试验研究,阐明了氧化镁水泥的膨胀特性与机理,并着重论述了微膨胀混凝土的体积变形,证明氧化镁水泥混凝土的长期变形性能是稳定的。通过工程验证,氧化镁的膨胀特性,掺合料质量与掺量都是可控制的。在工程中应用氧化镁延迟性微膨胀水泥,是坝体混凝土温控防裂的极其有效措施,也是理想的防裂新材料。     

水工混凝土裂缝机理与防裂技术述评

水工混凝土裂缝产生的机理及防裂措施的研究是人们关心的问题。文章就温度梯度、湿度梯度等产生裂缝的主要影响因素作扼要阐述，并探讨水工混凝土的防裂技术。     

石山口水库闸墩施工期温度分析

分析了混凝土闸墩温度裂缝产生的原因、温度变化和温度应力发展过程。对石山口水库闸墩中增设膨胀混凝土带后的施工期温度进行了实时监测,为了解混凝土水化热温度变化规律提供了实测依据,并与普通混凝土闸墩进行对比。结果表明,在闸墩中增设混凝土膨胀带效果良好,为混凝土闸墩施工期防裂提供了一种新的方法。     

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。     

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.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

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.     

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.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.