空冷平台施工质量及进度的提高

人类水资源的严重缺乏,使得电厂设计中对空冷技术广泛采用。如何在施工中提高空冷平台施工质量,加快空冷平台施工进度,成为电建施工单位一个重要的研究课题。空冷平台结构施工分为基础施工和柱段施工。柱段施工中有钢筋施工、模板施工、埋件施工、混凝土施工等几种工序。在基础施工中,采用单个基础开挖,从而提高施工进度和节省施工成本;在柱段各个施工工序中工序及施工内容方面提出合理的施工方法和好的管理方法,能提高工程的施工质量,加快施工进度,并能节省施工成本。     

隧道大管棚施工技术分析

对隧道大管棚施工技术进行了概述,并对大管棚施工过程中洞身施工、边仰坡施工、围岩施工、钻孔施工等关键环节的控制进行了论述,归纳总结了施工中需注意的问题,以期从根本上保证大管棚的施工质量。     

浅谈高等级公路施工中的过程控制

结合工程项目施工中过程控制的重要性,就高等级公路施工中施工准备控制、施工过程控制、施工安全控制分别进行了说明,从而确保施工质量,消除质量通病。     

浅析临地铁、高架深基坑施工技术

在邻近地铁、高架和处在闹市等地里条件下进行深基坑施工,如何控制好开挖中维护变形是工程中的关键技术,以上海南站附近的中星城项目为例,绍施工中采用的深基坑施工技术,介绍施工过程中深基坑施工技术、从施工规划、设计、施工、围护到降水都采用了严格控制变形措施,实践证明,该技术应对得当,圆满解决施工中的难题,确保了工程的顺利进行。     

房屋施工中技术节约措施的应用探讨

针对房屋施工过程中机械设备、施工用水、施工原材料等方面存在的浪费现象进行了分析,探讨了房屋施工过程中技术节约的具体应用,提出施工企业应从施工过程控制、施工后期分析等方面入手,合理控制施工成本,以减少经济损失。     

六安市淠史杭大桥索塔施工技术

索塔施工中其施工操作平台、测量的精准定位以及上横梁等施工难度大,文章结合六安市淠史杭大桥索塔施工,介绍索塔施工方案、施工工艺及施工控制要点等,施工中通过采用新工艺、新方法,取得了良好的效果。     

建筑外墙装饰施工技术研究

介绍了当前建筑外墙装饰施工中比较常用的技术手段,如外墙基层处理技术、抹灰施工技术、涂饰施工技术、门窗施工技术、外保温施工技术、玻璃幕墙施工技术、饰面砖施工技术等,探讨了建筑外墙装饰施工中需要注意的一些问题,从而为类似工程提供借鉴。     

建筑施工技术及现场施工管理探讨

从钢筋施工、模板布置、混凝土施工等方面,介绍了建筑工程中常用的施工技术,针对现场施工过程中存在的问题,从施工人员安全意识、施工管理制度、成本管理三方面阐述了现场施工管理措施,从而保证建筑工程的整体施工质量。     

桥梁挂篮悬臂浇筑施工技术

在桥梁工程施工过程中,挂篮悬臂浇筑施工是一种常用的施工技术,具有施工简便、结构整体性好、跨越能力强、不影响交通和通航等优点,因此被广泛应用于连续刚构桥、斜拉桥、悬索桥等桥梁工程施工中。文章以实际工程为例,对桥梁工程中挂篮悬臂浇筑施工技术进行了分析,总结了桥梁施工中悬臂挂篮技术要点,工程施工后取得了良好的施工效果,保证了挂篮悬臂浇筑施工质量。     

浅谈建筑工程文明施工管理

在施工的过程中,创造好的施工环境,就是以人为本的观念.在施工前创造良好的环境,施工过程中保持良好的环境,这是对自己生命的关爱,也是对别人生命的关爱.以前工程施工过程中忽视了文明施工,是因为施工管理存在薄弱环节,对文明施工的投入不够、规范不全、没有标准或标准不高.文明施工是技术的创新,强调文明施工,意味着施工过程中要不断采取新技术、新工艺、新方法,革新施工手段,完善技术设备,文明施工是企业发展的内在要求.     

冀东麻地岩体铷等稀有金属元素赋存特征

麻地岩体发生铷等稀有金属元素矿化,有形成大型稀有金属矿床的远景。为了查明麻地岩体稀有金属元素赋存特征,扩大找矿成果,依据区域地质资料和前人研究成果,开展野外地质调查与样品测试。在显微岩石学研究的基础上进行了电子探针分析,明确了麻地岩体稀有金属元素赋矿岩石的组构特征与矿物特征,分析了稀有金属元素的赋存状态,探讨了稀有金属元素富集机理。认为稀有金属元素偏向于在岩浆演化的晚期阶段富集,云母容纳稀有金属元素的能力强于钾长石,但钾长石的含量远大于云母,故岩体中钾长石的稀有元素总量高于云母。     

Predicting metal toxicity revisited: general properties vs. specific effects.

The present paper addresses the prediction of metal toxicity by evaluation of the relationships between general metal properties and toxic effects. For this, metal toxicity data were taken from 30 literature data sets, which varied largely in exposure times, organisms, effects and effect levels. General metal properties were selected on basis of literature reviewing of basic metal property classifications: used were the electrochemical potential deltaE0; the ionization potential IP; the ratio between atomic radius and atomic weight AR/AW; and the electronegativity Xm. The results suggest that toxicity prediction may be performed on basis of these fixed metal properties without any adoption to specific organisms, without any division of metals into classes, or grouping of toxicity tests. The results further indicate that metal properties contribute to the observed effects in relative importances which depend on specific effects, effect levels, exposure times, selected organisms and ambient conditions. The discussion strongly suggests that prediction should be by interpolation rather than by extrapolation of calibrated toxicity data: the concept here is that unknown metal toxicities are predicted on basis of observed metal toxicities in calibration experiments. Considering the used metal properties, the calibration covers the largest number of metals by the simultanuous use of Ge(IV), Cs(I), Li(I), Mn(VII), Sc and Bi in toxicity studies. Based on the data from the 30 studies considered, metal toxicities could be ordered in a relative way. This ordering indicates that the natural abundance of metals or metal ions in the Earth's crust may be regarded as a general comparative measure of the metal toxicities. The problems encountered in toxicity interpretation and ordering of toxicities indicate that control of the solution acidity, the metal's solubility and the metal's oxidation state may be key problems to overcome in future metal ion toxicity studies.     

优先流作用下的胶体-重金属共迁移试验研究

土壤中的重金属污染物大部分源自外界的工、农业排放,地表土层是重金属迁移至地下的必经途径。由于干缩和动植物活动,地表土中存在大孔隙,形成污染物运移的优势通道,在一些情况下,这些通道是重金属穿过包气带向下迁移的唯一途径。针对胶体对重金属具有较大吸附能力且在优先流条件下具有移动性,从而可能加快重金属污染物迁移这一问题,通过等温吸附试验确定了上海表层褐黄色粉质黏土与土壤胶体对重金属镉、铅的吸附特征,制备具有可重复性优先流特征的试验土柱,进行优先流条件下胶体-重金属共迁移土柱淋滤试验,分析得到胶体-重金属共迁移规律。试验结果表明,胶体对重金属的吸附能力明显高于粉质黏土。有胶体情况下,镉出流量是无胶体情况下镉出流量的1.49倍,铅的出流量是无胶体情况下的33.88倍,有胶体情况下土上吸附的重金属和孔隙溶液中的重金属浓度都低于无胶体的情况,更多的重金属随胶体向下迁移,优先流条件下胶体明显加快了重金属的迁移。虽然铅的源浓度和淋滤时间都大于镉,但铅的出流量仅约为镉的1/13,由于易发生吸附,铅在土中的迁移能力较弱。     

Application of Phytostabilization Technology in Remediation of Metal Mine Wasteland

The mining of metal mines has lead to serious environmental pollution and ecological damage, making remediation of mine wasteland urgent. Due to vegetation destruction, serious water and soil erosion and heavy metal migration and diffusion exist in the metal mine wasteland. Traditional physical and chemical treatment cannot solve these problems well. On the basis of analysis on status of metal mine wasteland, the application feasibility of phytostabilization technology in metal mine wasteland was analyzed. It was found that the phytostabilization could increase the vegetation coverage of metal mine wasteland in a relatively short time. In addition to solving the environmental problems, phytostabilization also created significant economic and ecological benefits.     

膨胀金属管轴向破坏的试验研究

膨胀金属薄膜广泛应用于世界各地的人行道设计和装饰用途。在文献中,很少有关于膨胀金属结构单元特性的信息。本文旨在研究压应力作用下方形和圆管状的膨胀金属薄膜的轴向破坏。当金属开始膨胀时,在金属片中可得到一种类似于钻石的单元,然后这些单元的特点是有两个几何轴线。一系列的试验测试可以印证膨胀金属的主轴和压力载荷之间角度的影响。从结果来看,根据轴线的方向有三种类型的破环模式:1)模式1的特点是塑性破坏机制;2)模式2会在个别元件处产生局部屈曲;3)模式3为管壁的整体屈曲。     

郑州东站大型金属屋面及细部构造施工技术

以郑州东站大型金属屋面施工为依托,分析金属屋面施工技术难点,介绍金属屋面施工顺序及施工控制要点,并结合施工难点,重点论述金属屋面细部构造控制措施,取得了良好的效果,为类似工程施工提供参考和借鉴。     

137Cs and 40K soil-to-plant relationship in a seminatural grassland of the Giulia Alps,Italy

The possibility of removing cadmium, copper, lead and zinc from Belgian loamy soil by a combination of sulfidisation pre-treatment and Denver flotation was investigated. The potentially available--sulfide convertible--metal content of the metal polluted soil was estimated by EDTA (0.1 M, pH 4.65) extraction and BCR sequential extraction. EDTA extraction is better at approximating the metal percentage that is expected to be convertible into a metal sulfide phase, in contrast to the sequential extraction procedure of 'Int. J. Environ. Anal. Chem. 51 (1993) pp. 135-151' in which transition metals present as iron oxide co-precipitates are dissolved by hydroxylammoniumchloride in the second extraction step. To compare the surface characteristics of metal sulfides formed by sulfidisation with those of crystalline metal sulfides, two types of synthetic sediments were prepared and extracted with 0.1 M EDTA (pH 4.65) in anoxic conditions. Separate metal sulfides or co-precipitates with iron sulfide were formed by sulfide conditioning. The Denver flotation of both types of synthetic sediments (kerosene as collector at high background electrolyte concentrations) resulted in similar concentrating factors for freshly formed metal sulfides as for fine-grained crystalline metal sulfides. The selective flotation of metal sulfides after sulfide conditioning of a polluted soil, using kerosene or potassium ethyl xanthate as collectors and MIBC as frother, was studied at high background electrolyte concentrations. The sulfidisations were made in ambient air and inside an anoxic glove box. The concentrating factors corrected by the potentially available metal percentage, determined by 0.1 M EDTA extraction, lie between 2 and 3. The selective flotation of these finely dispersed, amorphous, metal sulfides can possibly be improved by optimising the bubble-particle interaction.     

Microwave response characteristics and influencing factors of ores based on dielectric properties of synthetic samples

In order to understand the influence of different factors on the microwave response characteristics of ores, the effects of electrical conductivity, metal mineral content, compactness, metal mineral distribution, microwave frequency and temperature on the dielectric properties of synthetic ores (metal mineral and quartz) were studied. Microwave heating tests were carried out on three types of natural ores (Hongtoushan copper ore, Sishanling iron ore and Dandong gold ore) with significant differences in metal mineral contents. The test results showed that under microwave irradiation, the stronger the electrical conductivity of the metal minerals, the smaller the penetration depth in synthetic ore. For those metal minerals with lower electrical conductivity, the microwave absorption coefficient of the synthetic samples increases with increasing metal mineral content. For those metal minerals with higher electrical conductivity, the microwave absorption coefficient of the samples first increases and then decreases as the metal mineral content increases. When the metal minerals are distributed in layers, the penetration depth is much less than that given a uniform distribution. The penetration depth in the sample at microwave frequency of 915 MHz is greater than that at 2.45 GHz. The higher the electrical conductivity of metal minerals used in synthetic ores, the higher the high-temperature sensitivity of electromagnetic shielding coefficient (0 °C–500 °C). The Hongtoushan copper ore with high metal mineral content exhibits obvious size effect. The effects of ore structure and crystal particle size on the distribution characteristics of microcracks were discussed. Based on the test results, a quantitative prediction model of microwave sensitivity of ore was proposed, which provides guidance for the prediction of ore heating effect and the selection of microwave heating sequence of ore.     

承德黑山钒钛磁铁矿矿集区土壤重金属空间结构特征与生态风险评价

矿区土壤重金属来源、空间分布特征对矿山周围的生态环境脆弱区土壤环境保护、修复以及生态风险评价具有重要意义。本文以承德市隆化县韩麻营镇黑山钒钛磁铁矿所在小流域为研究区,利用地累积指数法、内梅罗污染指数法验证矿区周围土壤重金属污染程度,利用潜在生态危害指数法对土壤重金属的生态环境风险做了全面评价,利用变异函数、相关性分析、金属元素主成分和聚类分析等方法明确了研究区重金属来源及空间分布特征。研究结果表明:研究区土壤中重金属元素Mn、Ti、V、Zn、Co、Cu、Mo、Cd和SOM的平均含量均高于河北省背景值;重金属元素As、Cr、Ni、Sb、Pb的平均含量均略低于河北省背景值;土壤重金属元素的空间分布十分均匀。研究区大量土壤重金属元素为轻度污染,少量为中度污染,只在极少量的局部地区土壤重金属元素Ti、Cu、Co、Hg、Cr显示出重污染特性。研究区整体处于较清洁水平,并且研究区土壤重金属元素高值点主要分布在矿区周围和人类活动区域,钒钛磁铁矿矿区及其伴生矿物和人类生产活动对重金属元素含量分布有较大影响。     

Predicting metals partitioning in wastewater treatment plant influents

Interactions of heavy metals with primary sludge particulates were investigated using batch equilibrium metal uptake experiments. Results showed that metal uptake by primary sludge is significantly affected by pH. A mathematical model was developed to describe metals partitioning as a function of pH. The metal adsorption constants were determined. Results showed that for the same metal ion, the values of metal adsorption constants for primary sludge samples collected from different locations and at different times were in the same order of magnitude. Therefore, the adsorption constants were normalized and calibrated using field data. For Ag(I), Cd(II), Co(II), Cr(III), Cu(II), Ni(II), Pb(II), and Zn(II), the calibrated values of adsorption constants (logK(S)) are, respectively, 4.4, 5.1, 3.6, 4.5, 4.6, 3.6, 6.0, and 6.0. These constants can be used to predict the metal partitioning in plant influents and metal removal in primary treatment processes.