基于坡面冲刷的荆江典型岸坡稳定性分析

针对荆江典型二元结构的岸坡,采用横向冲刷计算公式探讨了不同水位升降阶段中,水流流速和含沙量对岸坡横向冲刷速率的影响以及岸坡断面形态的变化规律。在此基础上基于饱和-非饱和渗流理论,利用SEEP/w程序建立了二维非稳态渗流模型,模拟了其渗流场在水位升降条件下的变化过程,并基于摩根斯坦法计算分析了在考虑与不考虑坡面冲刷2种条件下岸坡稳定性的变化规律。结果表明:在水位上升期,当不考虑坡面冲刷时,岸坡稳定性是随水位上升而增大的,但当考虑坡面冲刷后,岸坡坡度逐渐增大,岸坡稳定性随水位上升而减小;在水位下降期,岸坡稳定性随水位下降而减小,且考虑坡面冲刷的安全系数下降速率明显大于未考虑冲刷时的情况。因此洪水期与水位下降末期是岸坡失稳的危险期,需重点监控。     

库岸边坡渗流及稳定性分析

库岸边坡常因受到库水位周期性波动的作用而失稳。传统的饱和土渗流及稳定分析方法无法正确描述水位升降过程中岸坡内孔压场的动态变化及其对岸坡安全系数的影响规律。本文从非饱和土的渗流和抗剪强度理论出发，分析了水位升降时土质岸坡的渗流规律及其稳定性的变化规律。通过选取典型的土性参数，对黏土、粉土和均质砂岸坡进行饱和-非饱和渗流分析，得到水位升降过程中岸坡内孔隙水压力场，再引入极限平衡方法，考虑基质吸力对非饱和土抗剪强度及岸坡安全系数的贡献，进行岸坡稳定性分析。分析表明，土体的饱和渗透系数和土水特征曲线共同决定了水位升降时岸坡内孔隙水压力的大小及分布，水位升降情况下岸坡安全系数的变化规律也与岸坡土体的渗透特性有关。     

汾河水库库岸塌岸机理与治理措施

水库塌岸造成库岸植被破坏,水土流失加剧,库岸坡失稳使库区农田减少,库区左岸公路路面裂缝,路基冲刷,直接影响当地的经济发展和社会秩序,因此应对库岸的坍塌机理和治理措施加以重视.汾河水库主要为黄土质岸坡,经分析认为,汾河水库塌岸主要是由于库水位变化、冻融、库水浸泡、风浪冲击,水流浸蚀以及干湿交替等因素造成的,针对塌岸形成特点,提出相应的治理措施.     

永嘉县瓯江治理工程Ⅲ标防洪评价分析

文章在阐述永嘉县瓯江治理工程Ⅲ标概况及水文气象、洪水特性的基础上,进行了水流平行于岸坡产生的冲刷及水流斜冲防护岸坡产生的冲刷深度的计算,以及河道护岸抗冲能力和堤防渗透稳定性的评价。     

绿化混凝土块体在河道护岸中的运用

河道作为输水的载体，沿线河床坡面土质各异．同时坡面上水位不断变化，加上风浪和水流的冲刷，会造成对坡面不同程度的破坏，随着水土流失逐年增多。河床也会逐渐淤塞、抬高。从而减少了过水断面，降低输水能力。用绿化混凝土块体作为护岸，既可保护岸坡稳定，从而减少风浪和水流对岸坡的冲刷、侵蚀，又可利用无砂混凝土块体所形成的孔隙。进行吸咐水份、养份，在块体表面及块体之间的孔隙填充复合土进行植     

河流冲刷作用下堤岸稳定性研究进展

分析河流冲刷作用下堤岸土体起动时的受力特点和冲刷破坏机理,概括国内外近岸水流冲刷力的分布与计算、堤岸土体抗冲力确定、河岸土体横向冲刷计算方法等研究成果,分析和评价河流冲刷作用下堤岸边坡稳定性研究进展。指出进一步研究的问题和研究方法:必须将堤岸边坡稳定分析与河流冲刷作用同时考虑,建立包含河流冲刷力的堤岸稳定分析力学模型;开展堤岸稳定分析的三维数值模拟;利用有限元法预测堤岸边坡破坏发展过程,分析变形与稳定的内在联系;将水上岸坡、水下岸坡以及坡脚和河床作为一个整体,进行堤防稳定的渗流场与应力场耦合分析。     

基于BSTEM的长江中游河道岸坡稳定性分析

以长江中游荆江出口熊家洲至城陵矶段典型断面为例,利用河岸稳定性与坡脚侵蚀模型(BSTEM)计算了2个典型断面在不同自然条件下的岸坡形态、水位条件、坡脚横向冲刷距离、植被类型及有护岸工程条件下河岸稳定的安全系数,分析了这些因素对河道岸坡稳定性的影响。结论表明:水位变化对河岸稳定性有重要影响,高、低水位岸坡稳定性与河岸组成密切相关,退水速率较快时,安全系数大幅度减小,易引起崩岸的发生;不同岸坡形态下河岸安全系数也不同,均随着坡脚横向冲刷距离的增大而减小;坡面实施护岸工程与植被覆盖会增加岸坡的稳定性。     

关于大凌河河岸稳定性的研究

在天然河道中,由于水流和岸坡的相互作用会导致河岸失稳,甚至造成河岸崩塌。为了保证河道安全与生态平衡,同时,也为了保证居民正常的生产生活,对河岸稳定性进行研究是十分必要的。多方法、多断面、多指标相结合的方法能弥补一般稳定性分析方法的不足。运用Trimble Juno SC高精度手持GPS、实地勘测及取样实验等多种方法,对大凌河河岸17个断面岸坡倾角、河岸高度、河岸基质类别、坡脚冲刷强度和岸坡植被覆盖率稳定性指标进行分析评估。结果表明大凌河河岸整体稳定性较好。分析结果能为将来河岸加固和防护提供依据和参考。更多还原     

基于 BSTEM 的长江中游河道岸坡稳定性分析简

 以长江中游荆江出口熊家洲至城陵矶段典型断面为例,利用河岸稳定性与坡脚侵蚀模型(BSTEM)计算了2个典型断面在不同自然条件下的岸坡形态、水位条件、坡脚横向冲刷距离、植被类型及有护岸工程条件下河岸稳定的安全系数,分析了这些因素对河道岸坡稳定性的影响。结论表明:水位变化对河岸稳定性有重要影响,高、低水位岸坡稳定性与河岸组成密切相关,退水速率较快时,安全系数大幅度减小,易引起崩岸的发生;不同岸坡形态下河岸安全系数也不同,均随着坡脚横向冲刷距离的增大而减小;坡面实施护岸工程与植被覆盖会增加岸坡的稳定性。     

刘家沟水电站溢洪道消能结构形式优化试验研究

为改善刘家沟水电站溢洪道消能形式、减小下泄高速水流对河床和岸坡的冲刷破坏,通过对溢洪道不同消能方案的对比试验研究,提出了岸坡分散水流冲刷河床的消能设计方法,进一步试验验证该方案在泄流流态和消能效果方面都达到了令人满意的效果。     

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。