锦屏一级高拱坝整体稳定分析与评价

介绍了锦屏一级高拱坝针对复杂地基的系统加固处理方案,并结合三维非线性有限元数值仿真分析和超载地质力学模型试验,分析了高拱坝的坝基变形、基础的破坏特征、点安全度及整体稳定性;考虑坝基岩体高应力和高渗压作用下,试验研究了软弱结构面可能的降强幅度,并通过综合法地质力学模型试验,揭示了大坝与基础破坏的另一种模式。综合三维数值计算和地质力学模型试验研究成果,依据评判准则,锦屏一级高拱坝整体稳定安全度较高,可满足设计要求。     

尾水岔管在调压室后交汇的水电站小波动稳定分析

基于刚性水锤理论,结合实际工程水道布置,考虑调压室阻抗作用以及实际水轮机和调速器特性,对采用尾水岔管室后交汇布置型式的水电站推导了水力机械系统小波动稳定性分析状态方程。运用稳定性理论,分析了电站的小波动稳定性,并利用基于特征线法的水电站过渡过程数值模拟进行验证,两者结果基本一致。随后研究了该类型调压室面积及阻抗孔口对系统稳定域的影响。结果表明:调压室面积越大,阻抗孔口面积越小,系统越稳定;当调压室设计面积超过稳定断面面积时,进一步增加调压室横截面积,对系统的稳定性并无多大改善,而当面积小于稳定断面面积时,系统的稳定域大幅度减小;阻抗孔口的尺寸会影响调压室的稳定断面面积,阻抗孔口尺寸越小,对应调压室所需的稳定断面面积越小。     

乌东德水电站右岸拱肩槽边坡稳定性研究

在对拱肩槽自然边坡工程地质条件详细调查的基础上,采用工程地质宏观分析和数值计算相结合的研究手段,对拱肩槽人工边坡整体稳定进行了系统研究;通过结构面组合分析,提出了人工边坡可能出现的块体失稳模式;从块体稳定性影响因素入手,建立了块体稳定性评价标准,并评价了块体的稳定性。工程地质宏观分析表明：拱肩槽边坡整体稳定性较好,数值模拟计算结果显示人工边坡变形特征不突出、稳定系数较高,人工边坡可能出现的块体多处于基本稳定状态。研究成果为工程设计与施工提供了重要依据,并对类似工程提供了可借鉴的经验。     

STATCOM控制的电力系统稳定性分析

基于哈密顿系统理论，将含有STATCOM的简单电力系统表示为标准的哈密顿系统，推导了该系统的哈密顿函数，并证明了所得到的哈密顿函数可作为判断系统稳定性的Lyapunov函数。根据该函数，提出了STATCOM控制的电力系统的暂态稳定分析新方法。对含有STATCOM控制的简单电力系统的数值仿真结果证实了这一方法的有效性。     

总体矩阵法在水电站频率调节稳定性分析中的应用

水电站输水发电系统稳定性的分析是电站设计和运行中的关键问题。水电站输水发电系统稳定性的分析以往多采用基于传递函数法的理论分析和数值仿真,但当管道系统较为复杂时,如一洞多机输水发电系统,则不易推导系统的传递函数,也不易建立仿真模型并得到较为准确的稳定域。针对上述问题,首先推导了机组阻抗表达式,然后基于水力系统振动特性分析方法,建立输水发电系统总体矩阵,并以最大衰减因子σmax是否小于0作为稳定性的判别依据。为了验证提出方法的准确性,采用总体矩阵法对两个工程实例进行了计算分析,在单管单机模型中与基于传递函数法和Simulink数值仿真的计算结果进行了对比;在一洞四机模型中与Simulink数值仿真的计算结果进行了对比。结果表明,总体矩阵法能够准确求解复杂输水发电系统的稳定域,并可通过修改系统各个模块相应的传递矩阵排列顺序而适应不同的电站布置形式,极大地方便了水电站运行稳定性的计算与分析。     

强不规则地形上浅水二维流动的数值计算研究

浅水流动数值模拟技术取得了显著进步,已能够有效地捕捉激波,但是应用于强不规则地形时计算困难,其原因在于:陡峭坡面上水流重力作用对数值稳定性有重要影响.采用简单的算子分裂法,即使是时间步长满足CFL稳定性准则,也可能致使计算不稳定,或者要求远比CFL稳定性准则更加苛刻的时间步长,从而严重影响计算效率.本文建立对强不规则地形和一般地形条件均能保持高效率的浅水二维数学模型:基本控制方程采用二维浅水方程;在空间上采用能捕捉激波的WAF TVD二阶精度格式;在时间上采用三阶TVD龙格库塔法,并采用自适应步长满足数值稳定性要求.将该模型应用于冰湖溃决洪水的模拟,试验结果表明:该文模型从本质上解除了强不规则地形对时间步长的约束,与现有数学模型相比,计算效率达到数量级上的提高,为强不规则地形上浅水二维流动数值模型的广泛应用(如高原与山丘区溃坝洪水数值预报等)提供了新的技术基础.     

频率死区对水电孤岛运行系统动态响应的影响

水轮发电机组的动态调节稳定性对电力系统至关重要。频率死区作为水力发电系统中重要的非线性环节,其对系统频率稳定性的影响机制值得深究。研究了频率死区对水电孤岛运行系统稳定性及其动态响应的影响。建立了含有频率死区的单机带负荷水轮机调节系统模型,应用描述函数法和时域数值模拟相结合的方法对该非线性系统的动态特性进行了分析。结论显示频率死区虽然不会减小系统稳定域,却显著影响了稳定、失稳、近似临界稳定各运行状态下水轮发电机组的动态响应规律。     

精密真空激光大坝变形测量系统中的激光漂移问题

为满足精密大坝变形测量的要求,通过数值模拟的手段,计算、分析了真空激光波带片衍射成像测量系统中激光束的漂移对系统测量造成的影响,得到若干有益的结论：采用合适的限位孔后可以消除激光束光轴侧移对测量造成的影响,激光束光轴的倾斜并不会影响像斑主极大的位置,但会影响次极大的位置,而且可能造成像斑亮度过暗而影响测量.通过对该实际系统的运行考核,证实了数值模拟结论的有效性和可靠性.     

电力系统暂态稳定预测控制的研究

提出了一种新的提高电力系统暂态稳定性的控制方法：预测控制方法。该方法 是用实测和预测分析相结合来取代传统方法中的解析推理，即以对发电机电磁功 率的实时测量来预测系统的稳定性，并根据预测分析的结果进行超前控制。数值仿真证实了 本控制方法的合理性和有效性。     

降雨条件下某堆积体边坡稳定性分析

堆积体边坡稳定性受诸多因素的影响,以西南深切河谷地区某堆积体边坡建立地质概化模型,通过有限元数值分析法和极限平衡法,对降雨条件下"转折型"堆积体边坡的稳定性进行分析。数值模拟结果显示:"转折型"堆积体边坡最大孔隙水压力出现在坡体后缘中部为452 kPa;最大位移量出现在坡体后缘为43.20 mm;最小稳定性系数为1.188。边坡稳定性分析认为:"转折型"堆积体边坡孔隙水压力上升较降雨时间具有明显的滞后性;边坡产生位移变形稍迟于降雨初始时间;坡体中部和前缘位移量变化差异异常与地形坡度"转折"紧密相关;降雨过程结束后稳定性系数较天然状态有所降低,长期持续降雨可能导致土体累积损伤最终失稳成灾;该堆积体边坡目前稳定性良好,并对该边坡提出了合理的防治措施。     

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.     

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。     

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。     

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.     

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.     

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.     

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.