粗粒料大型三轴试验中橡皮膜嵌入量对体变的影响及校正

在围压变化的应力路径上对粗粒料进行大型三轴试验时，需要有效地消除橡皮膜嵌入量对试样体积变形量测的影响，橡皮膜的嵌入量由试样侧表面的孔洞、膜间自由水、试样表面的疏松层以及橡皮膜张力的变化等复杂因素产生，通过试验的方法要精确地确定其大小、消除其影响是非常困难的。采用等向固结试验校正法，对多种不同筑坝堆石料的橡皮膜嵌入量进行了大型三轴试验研究，得到橡皮膜嵌入量的大小及其试验规律，发现橡皮膜嵌入量大部分在低围压的情况下发生，其与围压的关系可用双曲函数来表示，橡皮膜嵌入量占量测排水总量的发比在30％－50％之间，通过对橡皮膜嵌入量校正前后一组等应力比三轴试验成果合理性的讨论及该试验结果同压缩试验结果对应关系的分析，论证了等向固结试验校正法对粗粒料大型三轴试验的合理性。     

粗粒土试样橡皮膜嵌入影响的初步研究

针对直径为３００ｍｍ的粗粒土试样，通过在试样周围填充细砂的方法来消除橡皮膜嵌入的影响。饱和固结不排水往返加荷三轴试验表明，由于橡皮膜嵌入的影响，延缓了孔隙水压力的上升，使试样的认化应力增大１４％－１８％，在应用试验资料时，应予修正。     

三轴压缩试验中活塞摩阻和橡皮膜的影响

本文利用原状块样通过三轴压缩试验和无侧限抗压强度试验检验了活塞摩阻和橡皮膜对软粘土强度特性的影响.活塞摩阻和橡皮膜的约束将增加试样的不排水强度和应力—应变曲线的初始刚度;在固结不排水剪试验中主要影响总应力强度线的截距,对倾角的影响不大.     

动三轴试验中橡皮膜顺变性的影响及其校正方法

本文介绍在震动三轴试验中,采用试件表面涂液体硅橡胶的方法以消除橡皮膜顺变性的影响.通过涂硅胶和不涂硅胶两类试验的对比表明,橡皮膜顺变性效应阻滞了震动孔隙水压力的发展,使试验测得的动力强度偏大。文中最后提出比较简易的方法以校正橡皮膜顺变性的影响。     

空心圆柱仪主应力轴旋转试验副效应研究及对策

详细分析了采用空心圆柱仪进行主应力轴旋转试验遇到的若干问题,主要包括三个方面：空心圆柱试样制备及各向同性试样的获得;试验中尺寸效应、端部效应的考虑与消除;空心试样膜嵌入效应对排水、不排水试验结果的影响等.在系统研究的基础上提出了相应的解决方法,为合理试验成果的取得与修正提出了有益建议.     

颗粒材料定向剪切特性的空心圆柱离散元模拟

基于PFC3D离散元模拟平台构建空心圆柱型数值模型,研究了固定主应力方向条件下颗粒材料数值试样的定向剪切宏细观力学响应,重点分析了大主应力方向角对试样单调剪切特性的影响。数值建模中,采用"分离式簇墙"技术近似模拟室内试验橡皮膜的柔性边界效应,开发了顶部扭矩层颗粒旋转速度的"动态更新法"并较好地实现了剪应力的施加。结果表明,离散元数值模型能够较好地还原室内空心圆柱砂样定向剪切试验的应力路径和应力—应变响应;大主应力方向角α的变化显著影响数值试样的剪切强度,α=60°试样的峰值内摩擦角最低,且数值模拟得到的规律与已有的实际砂土室内试验规律相一致;数值试样剪切带的宏观演化在细观上可由试样内部局部孔隙比和配位数的变化规律来表征。     

土工布包裹对粗粒料三轴试验的影响研究

粗粒料三轴试验中,常使用在试样周围包裹土工布的方法防止橡皮膜被刺破。借助中型三轴仪,分别对粗粒料进行包裹土工布与未包裹土工布的常规三轴固结排水剪切试验,研究了土工布对试样强度和变形特性的影响。试验结果表明:对于相同的围压,包裹土工布试样的峰值强度(σ₁-σ₃)_f都比未包裹土工布的要大;低围压下,包裹土工布使试样强度提高很大,但随围压的增加,强度提高的幅值呈幂函数形式减小。对于线性强度指标,包裹土工布试样的黏聚力c是未包裹土工布试样的1.8倍,而内摩擦角φ则减小了1.8°。对于非线性强度指标,包裹土工布试样的φ₀是未包裹土工布试样的1.07倍,Δφ增加了5.5°。在相同围压下,包裹土工布试样的体积应变和侧向应变都比未包裹土工布试样的大;包裹土工布与未包裹土工布试样的体积应变差和侧向应变差受围压变化的影响较小。     

透明土中孔隙液体折射率、黏度系数与稳定性

为了探讨溶液作为制配透明土材料的可行性与稳定性,并为相关模型试验选用提供参考依据,针对二水溴化钙、焦磷酸钾、磷酸钾、六水氯化镁4种水溶型无机溶液和一种油溶型有机溶液(15号白油与正12烷混合物),系统测定折射率、黏度系数与溶液质量比之间的关系;采用目前模型试验中常用的溴化钙溶液、15号白油与正12烷混合物两种典型孔隙液体进行了孔隙液体对橡皮膜变形和抗拉强度、孔隙液体对透明土中固体颗粒材料的影响试验。试验结果表明,无机溶液折射率随质量比的增大呈线性增长,而黏度系数随着质量比的增大呈非线性增长;相同条件下溴化钙溶液和15号白油与正12烷混合物浸泡后橡皮膜长度变化率约分别为0.47%和37.81%,宽度变化率约分别为-1.09%和40.50%,抗拉强度分别降低约14.0%和89.4%;孔隙液体对熔融石英砂的影响较对无定形二氧化硅的影响要小,15号白油与正12烷混合物对固体颗粒的影响与溴化钙溶液基本相当。     

一台多用途的体变测量及控制系统

研制了一台多用途的体变测量及控制系统，这台设子可以与空心圆柱扭剪仪、静动三轴仪等多种试验设备相结合，既可用于测量饱和砂土完全排水试验中的体变，也可用于消除饱和砂土完全不排水试验中的橡皮膜嵌入效应。     

一台多用途的体变测量及控制系统

研制了一台多用途的体变测量及控制系统，这台设备可以与空间圆柱扭剪仪、静动三轴仪等多种试验设备相结合，既可用于测量饱和砂土完全排水试验中的体变，也可用于消除饮和砂土完全不排水试验中的橡皮膜嵌入效应。     

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.     

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.     

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.     

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.