考虑土工膜缺陷的面膜坝渗透稳定性分析

为研究土工膜缺陷的面膜坝在库水位骤降情况下的渗流特性以及上游坝坡的稳定性,利用Geo-slope软件建立了破损土工膜有限元分析模型,对土工膜不同破损部位以及破损尺寸进行了渗流要素和稳定性分析。结果表明:土工膜破损位置越高,尺寸越大,浸润线抬升越高,渗漏量越大,但后者影响明显小于前者;当库水位高程降落至土工膜破损高程时,存在一个浸润线突然下降的“突变”初始稳定安全系数随着土工膜缺陷位置的变高和尺寸的变大而变小,安全系数总体上呈现先下降,后趋于稳定的规律,但在库水位高程经过土工膜缺陷处,存在一个突然上升的过程。研究成果为面膜坝运行过程中的稳定性评价和治理提供了参考。     

平原水库复合土工膜缺陷渗漏影响因素数值分析

使用Flac3d数值模拟软件,以南水北调东线大屯水库为原型,建立平原水库复合土工膜缺陷渗漏数值计算模型,分析缺陷孔径、位置、水头高度及多缺陷联合作用对平原水库实际工程渗漏量的影响。结果表明:数值计算结果和室内试验结果吻合度较高,可用于实际工况分析;复合土工膜缺陷的数量和水头高度是影响复合土工膜缺陷渗漏的主要因素,其次为缺陷尺寸、缺陷间距和缺陷位置;复合土工膜缺陷尺寸较小和距坝脚较远时对复合土工膜缺陷渗漏量影响较小;复合土工膜缺陷渗漏量随缺陷数量和库水位的增加呈线性增长的趋势,当缺陷距坝脚小于100 m,且缺陷尺寸大于10 mm,同时缺陷间距较小时,应重点排查修补。     

平原水库土工膜防渗特性分析

复合土工膜防渗措施是解决平原水库渗漏问题的有效手段。为了研究平原水库土工膜防渗特性,以山东省清源湖水库为例,采用数值模拟与现场实测相结合的方法,建立了基于饱和-非饱和渗流微分方程的土工膜防渗围坝渗流有限元分析模型,并将计算结果与实测数据进行了对比。研究表明:铺设土工膜防渗后,非饱和区域显著增加,忽略非饱和区域会使得渗漏量计算值偏小、浸润线及溢出点高度计算值偏低,令设计者低估渗漏的严重程度,不利于坝体的渗流稳定;土工膜缺陷因素(如缺陷的位置、尺寸、数目及与其下垫层的接触情况)对渗漏量和围坝浸润线亦有较大影响;土工膜缺陷及土工膜与下垫层的接触情况主要取决于施工质量,在施工期对土工膜缺陷进行严格控制,可有效减少渗漏量,对平原水库的安全运行具有十分重要的意义。     

土体干密度对防渗土工膜膜下气场的影响

本文采用室内试验方法模拟水库现场实际情况,分析平原水库库盘土工膜防渗情况下,库底土体干密度对土工膜膜下气场的影响.结果表明:膜下土体干密度对膜下气场影响明显,干密度越大,库区膜下气场产生速率及气压越小.建议在平原水库库底土工膜防渗时要做好库区基底碾压,尽量选用干密度较大的土壤.     

土工膜缺陷对土石坝渗流特性的影响及控制措施

由于土工膜因缺陷导致的渗漏问题可能对土工膜防渗土石坝工程安全造成隐患,为此模拟不同的土工膜缺陷大小和位置,分别采用剔除单元法和渗透系数放大法对存在缺陷的土工膜坝面防渗土石坝进行饱和-非饱和三维渗流场有限元数值仿真计算,分析土工膜不同缺陷条件下大坝整体及局部渗流场变化规律。计算结果表明:土工膜缺陷渗漏仅对缺陷附近坝体局部渗流场分布产生较大影响,对大坝其他部位影响不大;土工膜缺陷位置越低,缺陷处水头越大,缺陷渗漏量增加越明显,并使缺陷处膜后坝体浸润线局部抬高。最后,针对土工膜缺陷渗漏提出了若干工程设计控制措施。     

土工膜防渗平原水库膜下气场数值模拟

以多相孔隙介质理论为基础推导了考虑孔隙中水气二相流的非饱和土固结理论方程,在一定的简化假设基础上编写了相应的有限元耦合计算程序。针对某土工膜全库盆防渗的平原水库进行了不同地下水位与库水位组合方案的三维有限元计算,通过整理库底和过渡平台两处膜下气压与地下水位及库水位变化关系曲线分析了土工膜下气压变化规律。计算结果表明:地下水位快速上升会引起膜下气压迅速增大,使得土工膜的气胀成为可能;当地下水位与土工膜间距小于1m时,膜下气压会随着库水位上升迅速增大。     

随机多缺陷条件下土工膜防渗土石坝渗漏特性

由于土工膜缺陷渗漏可能对土工膜防渗土石坝的防渗安全性造成隐患,采用饱和-非饱和渗流有限元理论,对坝面防渗土工膜多缺陷随机分布下的典型土石坝进行三维渗流场有限元模拟,合理考虑土工膜缺陷的数量、类型、位置、大小及其分布,重点分析土工膜的渗透量和缺陷渗漏量及膜后浸润面的变化规律。结果表明:与单缺陷条件下大坝渗流特性相比,坝面完好部分土工膜的渗透量变化不大,但多缺陷引起的渗漏量明显增大,导致大坝的总渗流量大幅增加。多缺陷会引起膜后坝体浸润面整体抬升,但局部浸润面高度变化与缺陷位置和数量明显相关,所在剖面缺陷位置越低,数量越多,浸润面抬升越明显。另外,膜后垫层水头局部分布规律与相邻缺陷渗漏的交叉效应相关。     

库水位下降速率对土石坝稳定性分析研究

库水位下降过程中,坝体黏性土对水份的吸力作用使得黏性土体内的水份不能及时消散,造成黏性坝体内水位高于库内水位,所发生现象对坝坡渗流、稳定与应力均产生较大影响.以大禾田水库为例,基于饱和-非饱和渗流理论,采用二维有限单元方法,分析库水位下降后的渗流稳定、应力及水压荷载作用下位移变形,分析库水位下降速率对土石坝稳定性的影响,研究结果对水库调度运行管理有一定的指导作用.     

瀑河水库坝基渗流稳定分析及处理措施

瀑河水库自建库以来，多次发生坝基渗漏、坝后管涌和下游沼泽化等渗流破坏现象。通过对工程地质的分析，提出引起坝基渗流破坏的几处薄弱地带。经过渗流稳定理论计算，预测在高库水位条件下主副坝均存在渗流破坏的可能性。为消除大坝可能出现的渗流稳定安全隐患，建议在坝前增设土工膜水平防渗；在主坝段增设坝后贴坡排水。     

大屯水库土工膜气胀变形影响因素分析

大屯水库围坝坝基采用库底全铺土工膜的水平防渗方案,在地下水位、土工膜损伤、温度等因素的影响下,膜下非饱和土层气场会发生变化,产生土工膜气胀甚至胀破现象。为分析大屯水库气胀变形影响因素,将土工膜气胀受力变形简化为环向约束条件下的土工膜气胀变形,研制了环向约束条件下土工膜气胀变形试验设备,开展了土工膜气胀变形影响因素的试验研究。研究表明:试验设备的孔径、加载速率、土工膜厚度是影响土工膜气胀变形的主要因素,土工膜损伤、温度也对土工膜气胀变形产生一定的影响。     

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.     

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.     

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.     

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.     

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。