水工沥青混凝土动态抗压尺寸效应试验研究

为研究动态荷载作用下水工沥青混凝土力学性能的尺寸效应规律，在5℃的环境温度及10^-5/s～10^-2/s的应变率条件下，对直径为100 mm、高径比分别为0.5、1.0、1.5和2.0的水工沥青混凝土试样开展了单轴动态抗压试验研究，分析了应变率效应与尺寸效应对沥青混凝土动态抗压强度、弹性模量及破坏模式的影响。结果表明：应变率越大或试样高径比越小，试样破坏越显著；随着高径比的增加，抗压强度减小，而弹性模量增大；随着应变率的增加，抗压强度与弹性模量的动态增强因子呈非线性增长趋势。基于试验研究，综合考虑应变率效应与尺寸效应的协同作用，引入应变率影响因子建立了水工沥青混凝土动态抗压尺寸效应计算模型，并验证了模型的合理性。     

再生砖粗骨料混凝土基本力学性能试验研究

为深入了解再生砖粗骨料混凝土的基本力学性能,测试了5种再生砖粗骨料替代率的混凝土棱柱体抗压强度、应力-应变关系和静力受压弹性模量等基本力学指标。结果表明:再生砖粗骨料混凝土棱柱体受压破坏过程与破坏形态与普通混凝土类似;随着再生砖粗骨料替代率的增加,棱柱体抗压强度先增大后减小、静力受压弹性模量逐渐降低、单轴受压应力-应变曲线的峰值应变逐渐增大;提出了再生砖粗骨料混凝土棱柱体抗压强度与立方体抗压强度的换算关系以及单轴受压应力-应变曲线的拟合公式,为再生砖粗骨料混凝土的进一步研究提供了重要依据。更多还原     

温度场作用下水工沥青混凝土的力学稳定性研究

为研究不同温度场下沥青混凝土的力学性能,在0～20℃条件下对水工沥青混凝土进行了三轴抗压试验和三轴蠕变试验,获得不同温度场下的材料性能影响,并通过引入硬化参量进行温度修正,根据logistic函数建立不同温度场的沥青混凝土应力-应变本构模型.研究表明:沥青混凝土在0℃表现出明显应力软化现象,出现脆性破坏,随着温度上升,...     

海水冻融后轻骨料混凝土的双轴压压强度和变形性能

针对我国渤海湾北部海域轻骨料混凝土结构的工作环境和受力状态，进行了海水中不同冻融循环次数后轻骨料混凝土的双轴压压强度试验，考察了试件的破坏形态和表面裂缝的走向特征。根据试验结果，分析了极限抗压强度随冻融循环次数和应力比的变化规律，并在此基础上建立了考虑海水冻融影响的双轴压压强度准则。探讨了冻融循环作用后轻骨料混凝土的双轴压压变形性能，包括峰值应变、应力-应变关系随冻融循环次数和应力比的变化规律。研究结果说明，随冻融循环次数的增加各种应力比下的应力-应变关系曲线均逐渐扁平，峰值应力点明显下降并右移，说明混凝土的极限抗压强度逐渐降低。     

三级配大骨料混凝土双轴抗压性能试验分析

利用自行研制的大型混凝土静、动三轴试验系统,完成了5种应力比、4种应变率、3种含水状态（干燥、自然、饱和）的三级配大骨料混凝土双轴动态抗压试验。试验研究了含水率对三级配大骨料混凝土动态极限抗压强度的影响,并在此基础上提出考虑含水率影响的大骨料混凝土动态破坏准则。研究表明,饱和混凝土试件在高应变率下的强度明显提高,而在低应变率下强度则有所降低。在相同应变率下,极限抗压强度在应力比为1∶0.5时达到最大值。影响三级配大骨料混凝土试件破坏形态的主要因素为应力比,其动态极限抗压强度随含水率的增大而增大,而静态极限抗压强度随含水率的增大而减小;单轴受压状态下的变形明显小于双轴受压,试件的峰值应变随应变率的增大而减小。     

历经荷载后受硫酸盐侵蚀的混凝土力学性能

通过对历经荷载后受硫酸盐侵蚀的混凝土进行单轴压缩试验,研究了荷载水平和溶液浓度对混凝土力学性能变化规律及侵蚀机理的影响,并与历经荷载后受硫酸盐侵蚀高强混凝土的力学性能进行了对比分析。分析结果表明:随荷载水平的增大,未侵蚀试件的峰值应力、弹性模量和峰值应变均有减小趋势,而受浓度为5%和10%侵蚀试件的峰值应力和弹性模量均减小,峰值应变增大;相同荷载水平时,随溶液浓度的增大,混凝土的峰值应力和弹性模量减小,峰值应变增大;随着荷载水平和溶液浓度的增大,普通混凝土和高强混凝土的应力-应变曲线均有变饱满的趋势,普通混凝土的主要力学指标比高强混凝土变化更显著。研究结果可为在硫酸盐侵蚀环境下的受损伤混凝土结构设计提供一定的参考依据。     

再生透水混凝土应力——应变全曲线试验研究

以再生骨料替代率(0、30%、70%、100%)和养护龄期(3d、7d、28d)为变化参数,完成了不同龄期不同再生粗骨料替代率下再生混凝土的单轴受压应力—应变全曲线试验,分析了不同养护龄期及不同再生骨料替代率对再生透水骨料混凝土的破坏形态、弹性模量、应力—应变全曲线斜率及发展趋势的影响。研究表明,再生透水混凝土的破坏形态和普通混凝土相似,再生骨料替代率对破坏裂纹有影响,替代率越高裂纹越宽,龄期对破坏面与荷载垂线方向夹角相关,龄期越长夹角越小,不同龄期不同替代率下透水混凝土的应力—应变曲线和普通混凝土的类似,分为上升和下降两个部分,龄期对上升部分影响显著,龄期越长应力—应变曲线斜率越大,再生骨料替代率对下降部分影响较大,再生骨料增加试样弹性模量变低,下降曲线变陡。且再生透水混凝土的棱柱体抗压强度与立方体抗压强度的比值高于普通混凝土。     

浇筑式沥青混凝土应力应变关系试验研究

对以天然砂砾石作为骨料的浇筑式沥青混凝土在不同沥青用量和不同温度条件下进行三轴试验。结果表明:浇筑式沥青混凝土的应力应变曲线呈现出应力硬化形态,且随着沥青用量的增加、温度的升高,应力硬化现象更加明显,双曲线段范围增大;邓肯-张模型及修正邓肯-张模型的理论曲线与试验曲线均吻合较好,主要模型参数随沥青用量增加或温度升高均呈下降趋势。通过对比两种本构模型破坏偏应力随围压的变化情况发现,在较高围压情况下,随着围压的升高,修正邓肯-张模型的破坏偏应力趋于平缓,增幅小,而邓肯-张模型的破坏偏应力几乎呈线性增加,其值明显大于修正邓肯-张模型的破坏偏应力,因此修正模型更加符合浇筑式沥青混凝土的强度特性。     

地震应变率下水饱和度对混凝土动力压缩效应的影响

为揭示地震应变率下不同含水量混凝土的力学性能变化规律,采用真空饱水设备快速制备不同水饱和度混凝土试件以消除水泥进一步水化对试验结果的影响;进行了3种应变率下(10-5s-1、10-4s-1、10-3s-1)的单轴压缩试验,测试分析了应变率和水饱和度对混凝土的应力应变曲线形态、抗压强度、弹性模量以及峰值应变的影响规律与影响机理。研究结果表明,随着应变率增加,混凝土动态抗压强度增大、弹性模量增加、而峰值应变减小;随着水饱和度增加,混凝土在静载以及动载下的抗压强度绝对值减小,但动载作用时动力强度增长因子增大;应变率越高混凝土峰值应变随水饱和度增大而减小的趋势越明显。综合考虑应变率效应以及水饱和度的影响,提出了混凝土力学性能指标的经验计算公式,与试验结果有着较好的吻合度。     

不同温度下掺玄武岩纤维水工沥青混凝土劈裂试验研究

【目的】为了解温度和纤维掺量对水工沥青混凝土抗裂性能的影响，【方法】采用长度6 mm的玄武岩纤维，开展了0℃、5℃、10℃下的掺纤维沥青混凝土巴西劈裂试验，并利用数字图像相关技术(DIC)对试样表面变形进行测量。【结果】结果显示：试验加载初期，试样的水平向变形不明显，当达到峰值荷载后，试样在上下压条之间的直线上出现明显的水平向应变，与裂缝扩展路径相对应，且掺入纤维增加了裂缝扩展路径的曲折程度；相同温度下，沥青混凝土的劈裂抗拉强度随纤维掺量的增加呈先增大后减小的变化趋势，0℃时，掺量0.8%对应的劈裂抗拉强度最大，5℃和10℃时，掺量0.6%对应的劈裂抗拉强度最大；在0℃的低温条件下，掺入0.2%的纤维可提高沥青混凝土的破坏拉伸应变，然而，当温度升高到5℃和10℃时，沥青混凝土的破坏拉伸应变随纤维掺量的增加呈先减小再增大的变化趋势；沥青混凝土断裂能随纤维掺量变化规律同样受温度影响，0℃和10℃时，断裂能随纤维掺量增加而增大，且掺量为0.6%～0.8%时，断裂能最大，但5℃时，断裂能随纤维掺量变化不明显。【结论】结果表明：在不同温度下，掺玄武岩纤维沥青混凝土抗裂性能随纤维掺量的变化规律是不...     

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.     

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.     

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.     

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.     

Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera

River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35–90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m^?2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m^?2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60–80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept.     

Surveying for Water Resources

Abstract

A professional Land Surveyor (Geomatician) describes the Hydrogeologists' survey requirements of a major water resources assessment for the government of The Sultanate of Oman (1992 to 1996). The need for objective specifications is stated. Specialist terms like geoid, spheroid, Mean Sea Level are explained and how to relate spheroidal levels to the geoid. Methods like traditional survey, satellite survey, and photogrammetry are introduced. The paper encourages coordinated working for the benefit of water resource assessment and recommends employment of the professional land surveyor for major studies.     

浅谈优化Vray渲染在制作三维场景的应用研究

用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要.     

固结、渗流和沉积控制方程研究

本文从两相流体动力学的守恒方程出发，考虑固相、液相的相对运动，推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程，并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达，可导出用于大、小变形固结、渗流和沉积的简化方程，显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制，适用范围较广。依据实际问题的要求，作了不同形式的简化。     

四川省及重庆市中型水电站效益分析

该文分析了四川省及重庆市几座中型水电站的调查材料表明：四川省及重庆市中型水电站不仅在川渝主网和地方电网中起着很大的作用，并具有巨大的社会效益，同时还有综合利用效益，说明修建中型水电站的优越性．