水布垭混凝土面板堆石坝三维非线性抗震分析

坝高233m的水布垭混凝土面板堆石坝位于强震区，因此对大坝在强地震作用下的安全性进行评价是必要的。采用三维非线性有限元法分析方法对坝体在地震作用下的动力响应进行分析并对其安全性作出评价。计算采用的地震波为根据抗震规范的反应谱人工拟合的地震波，其水平向和竖向加速度峰值分别为0．1g和0．067g。分析结果表明，坝顶加速度反应显著放大，坝顶附近下游区加速度和动位移均大于上游区，特别是在水面以上较为显著，可能使坝顶下游侧发生局部滑动。在4／5坝高附近面板的拉应力较大，应充分考虑加强该区域面板的抗震性能。     

阿尔塔什水利枢纽工程混凝土面板堆石坝抗震工程措施及静、动力有限元计算分析

鉴于强震区200 m级超高混凝土面板堆石坝所面临的变形控制难、坝体抗震等级高、砂砾石覆盖层深厚等诸多设计难点,结合阿尔塔什混凝土面板堆石坝坝体结构、坝壳料设计,借鉴已建工程经验提出抗震工程措施。通过建立坝体、覆盖层的三维有限元模型,堆石料静力本构分析采用邓肯张E-B模型,动力本构分析采用等效黏弹性模型,分析了考虑抗震工程措施的坝体抗震能力。结果表明:坝体在竣工期、正常运行期、正常运行+地震三个工况下的变形规律合理。混凝土防渗墙和面板结构中最大拉、压应力均可满足所选混凝土材料的规范要求。坝顶下游坝坡设置浆砌块石护坡后可有效减弱该区域局部动力剪切破坏和浅层滑移。坝顶上、下游边坡布置阻滑钢筋网以及适当提高填筑料的相对紧密度、孔隙率,可以有效提高大坝坝坡的抗震稳定性和坝体抗震能力。研究成果以期为今后300 m级面板堆石坝工程设计上提供借鉴。     

潘口面板堆石坝地震反应与动力稳定分析

为了研究面板堆石坝在地震作用下的动力、变形特性及安全性,以潘口面板堆石坝工程为研究对象,用有限元法对其进行地震反应分析,重点研究加速度反应特性、震后残余变形及面板变形、坝体单元抗震安全性及下游坝坡的抗震安全性.分析结果表明,大坝整体抗震性能较好,满足给定地震下的抗震稳定性要求;坝顶及坝顶附近下游坡部分区域的加速度反应较大,并发生相对较大的永久变形,为该面板堆石坝工程抗震中的薄弱部位.     

强震区某沥青混凝土面板堆石高坝抗震安全性分析

采用三维非线性有限元法,对Ⅷ度强震区某拟建抽水蓄能电站坝高161 m的上库高沥青混凝土面板堆石坝开展静动力应力变形计算。结果表明：静力条件下大坝变形分布规律合理,蓄水期坝体水平位移和沉降量极值分别为62.64和151.85 cm,面板拉应变极值为0.56%;在Ⅷ度设防地震作用下,坝体顺沟谷向、坝轴向和竖向动位移极值分别为22.88、21.90和13.76 cm,加速度极值分别为12.31、12.26和12.14 m/s²,震后坝顶震陷极值为30.01 cm,震陷率为0.19%;在面板反弧段和挖填交界处为拉应变峰值区,极值为0.85%。综合评价大坝整体安全性能良好,地震时不会出现重大安全问题。     

紫坪铺大坝汶川地震震害分析及高土石坝抗震减灾研究设想

紫坪铺面板堆石坝作为"5.12"汶川大地震强震区高土石坝的典型,重点总结了其主要震害,包括坝体地震永久变形,面板的脱空与垂直缝挤压破坏和施工缝错台,下游坝坡局部震损,防浪墙等坝顶结构震损,渗漏量变化等;并针对本次汶川地震土石坝震害的特点,提出进一步开展有关高土石坝抗震减灾设计研究的一些设想,包括土石坝震害及地震资料的调研与获取,高土石坝动力破损特征与地震灾害机理研究,高土石坝地震安全评价与震害评估方法研究,以及高土石坝抗震加固及应急处置措施研究等.     

某高面板堆石坝地震反应特性分析

针对高面板堆石坝的结构特性,采用三维非线性有限元技术,对大坝的地震反应特性及抗震安全性进行计算分析。动力计算中坝体材料及覆盖层按照等效线性黏弹性模型考虑围压效应进行模拟,混凝土面板动力计算分析采用线性弹性模型,并依据考虑围压效应的残余体应变及残余轴应变的动应力-残余应变模型对某高面板堆石坝进行坝体地震工况下永久变形计算。计算结果显示:顺河向最大永久变形为15cm,竖直向最大永久变形为49cm,均发生坝顶位置,地震引起的竖向变形为坝高的0.4%;三维动力参数敏感性分析表明,堆石体的水平绝对加速度反应极值为9m/s~2,最大放大系数为4.2,堆石体、面板最大地震反应位于坝顶局部位置,存在明显的鞭稍效应,但坝体地震反应的分布规律一致,坝体及面板抗震安全性较好。     

塔城心墙堆石坝地震反应分析

 塔城砾石土心墙堆石坝最大坝高 315 m ,地震动作用下,坝身特别是坝体上部容易出现严重裂缝或者坝坡失稳等问题。为了考察高土石坝经历高震级地震时的抗震性能,坝体及覆盖层材料采用 Hardin 非线性动力模型,在三维非线性静力分析基础上,用时程法对大坝进行地震动力分析,以揭示在 Taft 三向地震波的作用过程中坝体中加速度、动位移、动应力的分布及其地震永久变形和液化情况。坝体非线性仿真结果表明,在设防烈度地震作用下,在坝体最大断面上,坝顶动力放大系数为 2.5 左右, 1/2 坝高小范围内有拉应力出现,坝体沉陷及向下游水平位移较大,坝踵坝趾局部有一定的液化可能。     

二滩拱坝地震响应的动力模型试验研究

二滩双曲拱坝的动力模型试验在大型模拟地震振动台上进行。研究了在实际地震波作用下,坝体、水库和地基的相互作用影响,坝体抗震安全度,动水压力分布和拱坝在强烈地震下的破坏机理。研究结果表明:1.高拱坝的最大动应力是拱应力,位于上游坝顶中间部位。下游坝顶中间部位和2/3坝高部位以及坝踵是抗震薄弱部位。2.紧靠拱坝上游面的山体形状对坝面动水压力值的影响较大,故对于坝前地形复杂的水库,应模拟一倍坝高长的自然地形。3.满库时,拱坝前几阶固有频率对库水位的微小变化非常敏感。4.拱坝在强烈地震下的破坏在瞬间完成,主要是中上部的脆性开裂。     

密松水电站面板堆石坝抗震设计与安全性评价

密松水电站面板堆石坝属于超宽河谷的面板堆石坝,其抗震分析还缺少相应的工程经验。针对面板堆石坝在强震中易产生坝体永久变形过大及面板易破损等问题,采用拟静力法和有限元时程动力法,分析了堆石坝的加速度和应力反应、面板应力、接缝变形、坝体地震残余变形以及坝坡的动力稳定性,对大坝的抗震安全性进行了综合评价。结果表明,在设计与校核地震作用下,坝坡稳定性满足规范要求,坝体永久变形与同类工程相当,面板应力状态满足抗震安全要求,面板接缝变形在止水结构允许范围之内。     

高面板坝护坡面板的钉结抗震加固效果分析

对强震作用下坝体下游护坡面板钉结加固前后的受力状态和稳定性进行分析,推导得到面板抗滑稳定安全系数的表达式。基于某面板堆石坝的动力有限元计算结果,得到坝顶至坝顶以下21 m范围内的护坡面板会沿坝坡的法线方向滑动逸出,应采取钉结措施对面板进行抗震加固。利用以往钢筋在堆石料中拉拔试验的研究成果,研究面板尺寸和钢筋嵌入深度对面板钉结加固措施的效果,结果表明,面板尺寸越小、钢筋嵌入深度越大,面板的抗滑稳定安全系数越大。     

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.     

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.     

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．     

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。     

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.     

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。