第二届国际软土工程会议模型专题综述

模型试验方法是探讨和解决岩土工程问题的一条重要途径，特别是土工离心模型，它借助于离心力场的作用，使模型土体中各点的应力与原型相等，从而满足模型相似律，在模型中能再现原型性状。更具有实用意义的是，软土层完成固结在原型中往往需花多年甚至几十年，而在模型中由于排水路径的缩短，仅需很短的时间。近年来国际上围绕软土工程开展了一系列的土工离心模型试验，重点探讨研究软土的特性和改良加固处理方法。第二届国际软土工程会议模型专题方面的论文充分体现了该领域的最新研究动态和发展趋势，在研究内容、试验模拟手段和分析处理方法等方面都有新的突破     

离心模型试验与试验技术研究

离心模拟是利用离心力场模拟地球重力场，用缩尺模型研究物体受重力加速度后的的各种物理现象。1869年法国科学院E．Phillips首先提出用离心力场代替重力场。1932年苏联莫斯科水力设计院建成了世界上第一台土工离心机。1935年美国哥仑比     

土工离心模型试验技术的一些进展

对近年来在土工离心模型试验技术方面取得的一些进展加以概括和总结,包括模型材料的选择，离心模型试验误差分析，数据采集系统的研制，动态模型技术，动力土工离心模型试验等方面，另外，还就其应用方面的一些进展作卫简单的评述。     

土工离心模型试验大流量供水系统设计研究

当前的土工离心模型试验的几种供水方式存在流量小、不稳定、测不准、造价高等问题,针对这些问题,研发了一套离心机大流量供水及控制系统。系统主要包括：上层供水系统、下层储水和供水系统、排水系统以及流量量测控制系统。系统采用环形水箱作为二级储水、供水箱,利用离心机旋转产生的巨大离心力驱动水流向模型试验箱内供水,同时采用离心实验专用孔隙水压力传感器来辅助监测流量,通过计算机控制布置在重力场与低离心力侧的电控阀门来实现流量的分级控制。该系统当前管路在50g离心力场下持续供水最大流量可达8 L/s, 100g离心力场下理论最大供水流量可达100 L/s,结合不同的模型试验箱布置,系统可开展降雨、库水位变动导致的滑坡、溃坝、枢纽泄洪消能等需水离心模型试验研究。     

土工离心模型试验数据采集系统

一、前言土工离心模型试验是将模型置于高重力场中,观测土工结构模型的性态。其用途通常为:(1)了解拟建或已建工程在各种载荷条件作用下的性态。即利用离心模型试验的结果通过模型律来预测原型相应的反应;(2)验证土工数学模型。土工离心模型试验是将土体和工程结构模型置于仿真的原体应力场的作用下进行观测,类似于原型观测,故可验证相应的数值计算结果;(3)了解工程体系的未知性态或破坏机理。这是某种     

土工离心模型试验研究的进展与思考

本文简要介绍了土工离心模型试验从提出概念到今天在试验设备、模型制作、量测仪器、相似比研究、数据采集、应用领域等几个方面的发展历程,并结合笔者参加离心模型试验的亲身体会,对离心模型试验今后的研究工作和方向,提出了自己的看法。     

无纺土工织物加固堤坝的离心模型试验

无纺土工织物加固堤坝的离心模型试验中,采用倾斜模型和对模型施加垂直荷载.试验结果表明:增加无纺土工织物的加筋长度能够加强堤坝的稳定.假设圆弧滑动面的稳定分析说明了与离心模型试验很好的一致性.     

土工离心模型试验技术的一些进展

对近年来在土工离心模型试验技术方面取得的一些进展加以概括和总结 ,包括模型材料的选择、离心模型试验误差分析、数据采集系统的研制、动态模拟技术、动力土工离心模型试验等方面。另外 ,还就其应用方面的一些进展作了简单的评述     

刚性桩复合地基离心试验插桩制模研究

土工离心模型试验是研究复合地基关键问题的前沿手段，饱和黏土工况下的刚性桩复合地基离心模型制作复杂，影响因素较多。基于多组刚性桩复合地基离心模型的制备过程分析，探讨了1g下插桩制模对离心模型地基抗剪强度的影响。试验结果表明：离心模型地基制样扰动与插桩方式相关，先引孔、后插桩有益于减少制样扰动。1g制模过程中，黏土模型地基的不排水抗剪强度有所损失，插桩制作扰动与1g下模型静置是导致饱和模型地基强度损失的主要原因，且复合地基上层软土抗剪强度的降低程度大于下部持力层。离心模型对比试验应充分考虑模型土样应力历史的相似性。研究提出了理想的刚性桩复合地基离心模型试验步骤，可为提升土工离心模型试验的精细化水平提供参考。     

离心场中陡倾顺层岩质边坡振动试验关键技术研究

为解决离心场中陡倾顺层岩质边坡振动试验的关键技术问题,设计了陡倾顺层斜坡的离心振动台模型,通过试验探讨了试验仪器设备的关键技术参数、动力相似关系、相似材料比选以及传感器的安装布置等内容,并确定了地震波的加载方案。同时为了得到可靠的试验结果,分析了离心力场中的误差、传感器的安装与误差问题和边界效应问题,结合以往经验对误差方法进行比选,并提出了相应的减小误差的方法。研究结果表明:离心振动台模型试验要进行合理的设计;离心力场中的系统误差可通过设计模型尺寸大小和选择模拟模型和原型应力保持一致的高度来减小;传感器测量误差可采用在传感器周围填充满砂土来减小;多层剪切层铝合金框架模型箱能够最大程度减小边界效应的影响。     

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.     

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。     

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.     

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．     

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.