非均匀沙床面阻力特性的实验研究

天然情况下，河流泥沙组成多为非均匀沙。河流床沙及其粒径组成的非均匀性是影响水流阻力的主要因素之一，研究床沙组成的非均匀性对水流阻力的影响，具有重要的理论和实际意义。本文在大量实验和实测资料的基础上，首次系统考虑床沙级配及其组成的非均匀性对水流阻力的影响，认识了床沙组成非均匀性对水流阻力的影响关系，初步得出非均匀性对水流阻力影响的规律，丰富了人们对床面泥沙组成非均匀性的认识，为进一步深入研究奠定了基     

非均匀沙床面阻力特性及计算方法

天然情况下，河流泥沙组成多为非均匀沙．研究床沙组成非均匀性对水流阻力的影响，具有重要的理论和现实意义．以Keulegan流速公式为理论依据，分析可靠的2174组试验和国外1404组河流实测资料，系统考虑庆沙组成的非均匀性对水流阻力的影响关系，建立了非均匀沙床面阻力系数的计算方法．通过长江中下游678组现场资料验证，得知计算结果有较高的精度，可供确定非均匀沙床面阻力时参考．     

天然河道不连续宽级配床沙特性及形成条件探讨

选取我国有代表性的几个河段对不连续宽级配床沙特性及形成条件进行了初步探讨,为不连续宽级配床沙运动规律研究提供了基础。认为不连续宽级配床沙特性为：泥沙粒径范围很宽,某一粒径范围泥沙较少甚至缺失,床沙粒径重量百分数具有明显的双峰分布特征。不连续宽级配床沙形成的一般条件为：河床床沙本身具有一定的不均匀性,河床有一定的覆盖层厚度,上游具有补给性的来沙条件,河段水流速度具有一定的变化幅度。     

沙波运动与床沙交换调整

冲积河流非均匀沙表层床沙粒径组成是影响水流阻力、输沙及河床冲淤的重要因素.表层床沙组成随着冲淤及与深层床沙不断交换而调整变化.本文分析提出沙波运动是床沙交换最基本最普遍的原因,提出了随冲淤及床沙交换床沙调整变化的计算关系.根据作者及其它水槽试验和河流实测沙波资料,文中总结得出了沙波高度、沙波运动速度及周期的新的计算公式,可用于估算床沙活动交换层厚度及交换速度,也可用于其它方面的分析计算.     

冲积河流长距离冲刷不平衡输沙过程初步研究

本文从悬移质扩散方程出发, 研究冲积河流长距离冲刷不平衡输沙过程. 对于天然沙质河流, 床沙均为非均匀沙, 由于较细泥沙的冲刷率总大于较粗泥沙, 因此在床面薄层内泥沙随冲刷迅速粗比, 致使挟沙力降低, 不平衡输沙距离比均匀沙情况大大延长. 文中同时提出了表层床沙粗化的概化计算模式及床沙交换速率计算公式. 床沙交换速率的大小是决定含沙量恢复饱和距离的重要因素. 本文对不同类型底部边界条件进行了计算比较, 并与黄河下游的实际冲刷资料进行了对比, 结果表明, 应用梯度型底部边界条件, 且在考虑表层床沙粗化中以作者提出的公式计算床沙交换速率, 则计算含沙量和实际符合良好.     

床沙代表粒径与输移泥沙中值粒径的关系

本文分析了输移泥沙床沙质中值粒径D50i的变化规律和计算方法，指出由于水流的分选作用，输移泥沙的中径D50i一般较床沙中值粒径D50为细，且相对中值粒径D50i/D50随床沙标准方差σg的增大而减小。还分析了床沙非均匀性对输沙能力的影响，结果在相同的D50条件下，输沙能力随σg的增大而增大。此外，对采用D50i作为床沙代表粒径的输沙能力计算进行了探讨，结果可以大大提高输沙能力的计算精度。研究表明，用于非均匀沙输沙能力计算的床沙代表粒径，不应是一个固定不变的粒径，床沙代表粒径及相应的沙重百分数应随σg的增大而减小，Einstein等建议的D35仅在σg值为1．5左右才适用。     

不连续宽级配床沙推移质输沙率特性试验分析

通过水槽试验对不连续宽级配床沙的推移质输沙率进行试验研究.深入分析、探讨了不同水流强度及不同床沙组成对连续与不连续宽级配床沙输沙率的影响.在已有研究成果的基础上,构造了考虑床沙不均匀性的相对水流强度表达式,着重研究了相对水流强度与推移质输沙率函数的关系.利用试验资料对提出的表达式进行回归分析,确定了有关参数.最终确定的...     

非均匀沙起动规律探讨

本文从分析非均匀沙的起动机理入手，在非均匀少度变化规律研究的基础上，确定床沙的可动层厚度，并用力学分析及泥沙颗粒分布的统计特性理论、解析几何方法，推出了非均匀潲起动流速的计算公式。对该公式用实测的床沙级配资料验证，所得的结果与实测的泥沙起动速一致。     

床面粗化层粒径级配的研究

本文研究了清水冲刷条件下宽级配非均匀床沙粗化的规律性。研究中不仅考虑了水流的紊动性和泥沙非均匀性对其起动规律的影响,而且还考虑了不同粒径泥沙起动引起水流相对脉动强度的变化。通过试验,分别就单峰型和双峰型初始床沙级配,给出了粗化后床面层粒径组成的计算方法,并与已有的试验资料和计算结果进行了比较。     

冲积河流悬移质泥沙与床沙交换机理及计算方法研究

本文在分析前人研究成果的基础上，从非恒定挟沙水流沙量平衡入手，建立了冲积河流悬移质泥沙与床沙交换关系表达式，并引入平衡冲淤物粒径的概念，对冲淤物粒径的计算方法进行了系统分析，提出了一整套计算非恒定挟沙水流悬移质泥沙与床沙交换的模式与方法，同时将该方法引用到数学模型中，采用黄河下游典型洪水进行了验证。     

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.     

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.     

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．     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.     

Statistical tools for thermal regime characterization at segment river scale: Case study of the Ste‐Marguerite River

Suitable thermal fish habitats are constrained by both maximum and minimum temperature tolerances. A multivariate and geostatistical approach was developed to estimate stream thermal characteristics at the river segment scale. Data from 22 temperature‐monitoring stations during summer 2007 were used to estimate monthly maximum temperature as well as thermal characteristics such as the number of events, the cumulative degree–days and the associated duration over specific temperature thresholds of 19 and 21°C. The probability of exceeding these temperature thresholds has also been interpolated. The methodology relies on the construction of a multivariate space using physiographic and hydrological characteristics of gauging stations as inputs in a canonical correlation analysis (CCA). A geostatistical interpolation technique, ordinary kriging, was subsequently used to perform interpolation in the physiographical space constructed using CCA. Results from this study were obtained for thermal characteristics estimated into two different interpolation spaces: (1) a 7 metrics space, and (2) an 8 metrics space. Cross‐validation technique has been performed and satisfactory results were obtained. Kriging thermal characteristics (magnitude and duration) into the 7 metric space for a 19°C threshold exceedance leads to best results with Relative Root Mean Square Error (RRMSE) ranging between 9.66 and 15.08%. The study shows that kriging in a multivariate space is a promising tool for water resources managers, especially in cases where risk mapping for lethal or sub‐lethal temperature thresholds may be required for a specific fish species. Copyright © 2010 John Wiley & Sons, Ltd.     

掺MgO混凝土的宏细观试验研究

利用MgO膨胀剂的延迟微膨胀效应能显著提高大体积混凝土的力学性能,产生的预压应力还能有效提高大体积混凝土抵抗温度开裂的能力,但目前对其微观机理研究不多。采用宏观与微观相结合的方式,研究了不同活性指数、不同掺量的MgO混凝土的力学性能,利用SEM/EDS微观分析手段揭示了MgO对混凝土性能影响的作用机理。试验结果表明：MgO取代部分水泥掺入混凝土中,混凝土的力学性能降低;掺量为4%~5%时,活性指数为100s的MgO混凝土的膨胀率大于活性指数为50 s的MgO混凝土;MgO混凝土的膨胀特性与Ca,Si,Mg,Al等元素的分布情况有关,掺入的MgO将改变界面区Ca,Si,Mg元素的富集特性,Ca元素和Mg元素更易于在界面区富集,导致混凝土宏观力学性能的降低。     

基于MIDAS软件探讨施工工序对深基坑稳定性的影响

基于武汉地铁名都站深基坑工程与水文地质勘察资料,建立了三维工程地质仿真计算模型。依据名都站深基坑开挖支护方案,利用有限元软件MIDAS的摩尔-库仑本构模型,对武汉地铁名都站深基坑施工过程中,不同施工工序下每步开挖之后,基坑的变形情况做仿真模拟计算,并对比分析其对基坑稳定性的影响。结果表明：基坑围护结构的变形情况与施工工序有很大的关系,施工工序越合理,上部土体变形越小,反之越大。因此,在基坑工程的施工过程中,要注重施工步骤的划分与合理安排,从而保证基坑工程的安全。研究成果为以后武汉地区基坑工程的施工设计提供了值得借鉴的经验。