粉煤灰和土的长期渗透特性试验研究

<正> 火电厂每年都产生大量粉煤灰,这些粉煤灰除少部分被综合利用外,大部分都贮放于灰场或用于工程回填。由于粉煤灰中含有有害元素,当粉煤灰与水接触后,灰中有害元素溶出并通过渗透扩散。在估算有害离子扩散范围及扩散量时,渗透系数是比较关键的参数之一,渗透系数选取的正确与否直接影响分析成果的合理性。目前,在进行灰场地下水污染分析时,采用的渗透系数一般为常规的短期渗透系数,不考虑渗透系数随时间变化的性质。     

凝硬和冻融作用对干贮粉煤灰的力学性质的影响

介绍了两种低氧化钙含量的粉煤灰和一种高氧化钙含量的粉煤灰在不同制样龄期条件的强度、渗透、压缩特性试验和冻融条件下的强度试验结果 ;分析了凝硬和冻融作用对干贮粉煤灰的力学性质的影响规律。试验结果表明 ,高氧化钙含量的粉煤灰的强度指标受上述两种作用的影响显著 ;低氧化钙含量的粉煤灰的强度指标在凝硬作用下也有所提高 ,但基本不受冻融作用的影响 ;干贮粉煤灰的渗透系数受凝硬和冻融作用的影响较小     

贮灰库渗流控制及三维等参元数学模型的应用

燃煤电厂粉煤灰的贮放多用水力冲填法,贮灰库内形成渗流场。本文从粉煤灰特殊的物理力学性质出发,阐明加强排渗设施,缩小贮灰库下游饱和区范围的重要意义,并分析了几类灰坝的排渗型式,指出贮灰库设计和研究的趋势;同时介绍了伽略金法和等参数单元在贮灰库排渗模拟中的应用,指出渗透系数的各向异性对贮灰库渗流的影响程度。模型采用了多种形态的等参元,用较高阶空间等参元模拟排渗干扰井群,效果良好。     

贮灰场固化粉煤灰防渗材料试验研究

粉煤灰是目前数量最大、对环境影响最为严重的一类固体废弃物。建设贮灰场是一项贮灰与环保工程,但贮灰场运行过程中出现的粉煤灰对大气和水源的污染是急待解决的问题。在对粉煤灰、膨润土、石灰性质及相互作用机理分析的基础上,通过对混合料抗渗、无侧限抗压强度、抗冻融循环、抗干湿循环以及抗酸碱环境等技术性能的试验对比,并采用满足贮灰场防渗要求的固化粉煤灰混合材料,从而为其推广应用提供了科学依据。     

压实粉煤灰的工程性质及龄期的影响

<正>一、前言 目前,我国各大火电厂对粉煤灰的处理一般采用水力管道输送,在平原或山谷中贮放。国外一些电厂采用了干贮灰的方法,即将干灰加水压实后贮放,这种方法对于缺水地区更有实际意义,干贮灰方法在我国还处于试验阶段。北京高井电厂所进行的干贮发现场碾压试验方法步骤是:用搅拌机将灰加水搅拌,用装有密封仓的专用汽车运至现场,再由推土机将灰     

两座电厂粉煤灰的强度特性及筑坝方法

<正>前些年建筑的贮灰坝,大都依据水利工程中土坝和堆石坝的设计原则一次性建造的。稍后改为使用当地材料建造初期坝和继后逐级建造的子坝。子坝的坝基为粉煤灰。由于库区内贮放的是水和灰,与通常的水坝有所差别。所以,若按挡水坝要求来设计,一般会有保守的一面。另一方面,粉煤灰比重小、颗粒细(平均粒径d₅₀一船小于0.1mm)、均匀、无粘性,饱和状态下受静力和动力作用都容易发生流动性的液化破坏。此外,采用的土、石坝料占用大量     

贮灰场的地震反应分析及抗震加固

燃煤火电厂湿法贮灰场的灰渣沉积层往往处于饱和松软状态,难以在其上建造子坝,且灰渣层在地震作用下极易发生液化,危及灰坝安全。笔者结合某些电厂贮灰场的子坝加高工程,在室内外试验的基础上,用有效应力的动力分析法计算了地震作用下贮灰场的动力反应,并提出了抗震加固措施。为类似贮灰场的抗震分析与加固指出了一条有效的途径。     

压实“干”粉煤灰的动力特性

<正>一、前言 将火电厂的出灰系统由传统的“湿法”改为“干法”(即由水力冲填法改为碾压法),其突出的优点之一是,可以大大提高粉煤灰坝的抗地震稳定性。本文报导了压实粉煤灰动力特性的试验结果,通过与水灰特性对比,证实了在地震区采用“干法”贮灰的优越性。     

粉煤灰的动剪切模量

笔者在自振柱仪上研究了国内三个电厂的粉煤灰动剪切模量特性。研究结果发现:动剪切模量随周围有效应力的增加而增加,随孔隙比的增加而减少。颗粒的尺寸、级配和表面形状也将影响剪切模量值。饱和度的变化将导致动剪切模量的改变。通过比较还发现:在相同相对密度的条件下,粉煤灰的动剪切模量约为砂土动剪切模量的30～60％。根据比较的结果我们认为,粉煤灰很有可能成为较好的地基隔震材料。     

水泥胶凝砂土动力特性研究

通过室内动三轴试验研究了砂土与水泥胶凝砂土在不同应力条件下的动力变形特性及抗液化特性,结果表明:胶凝材料的掺入显著提高了砂土在动荷载作用下抵抗变形的能力,在较低水泥掺加量条件下,胶凝砂土中砂土的动力特性仍占据主导地位,其动力特性仍可用沈珠江提出的砂土动力黏弹性模型来模拟;胶凝砂土的动模量比砂土大3倍以上,而抗液化动剪应力则为砂土的2倍以上,但初始变形量及累计动残余变形量值均较砂土大幅降低;胶凝作用对低应力状态更为敏感,应力水平越低,胶凝作用对砂土抵抗动力变形能力的提高越显著,随着胶凝材料掺入,浅层砂土已很难发生地震液化,深层砂土的液化破坏主要为变形破坏,但破坏时也累积了较大的动孔隙水压力。     

运用轻便动力触探仪测试粉煤灰工程特性

结合某粉煤灰筑坝工程 ,运用轻便动力触探仪对粉煤灰在碾压填筑方面进行了一系列现场试验 ,与几种常规原位测试手段进行了对比分析 ,结合该仪器开展了粉煤灰分层碾压密实度试验 ,在此基础上 ,分析了粉煤灰的岩土力学性质 ,尤其是粉煤灰的密实性。对比与常规原位测试所测得的力学参数 ,提出了一种运用所测的力学强度对粉煤灰的密实度进行间接评价的简单方法。     

Engineering properties of water/wastewater-treatment sludge modified by hydrated lime,fly ash and loess

The purpose of this research was to present engineering properties of modified sludge from water/wastewater treatment by modifiers such as hydrated lime, loess, and fly ash. The proper mixing ratio was determined to hold the pH of the modified sludge above 12.0 for 2 h. Laboratory tests carried out in this research included particle analysis, compaction and CBR, SEM and X-ray diffraction, unconfined compression test, permeability test, and TCLP test. The main role of lime was to sterilize microorganisms in the sludge. The unconfined strength of the modified sludge by fly ash and loess satisfied the criteria for construction materials, which was above 100 kPa. The permeability of all the mixtures was around 1.0 x 10(-7) cm/s. Extraction tests for hazardous components in modified sludge revealed below the regulated criteria, especially for cadmium, copper, and lead. The present study suggested that the use of lime, fly ash, and loess be an another alternative to modify or stabilize water/wastewater treatment sludge as construction materials in civil engineering.     

Optimization of fineness to maximize the strength activity of high-calcium ground fly ash – Portland cement composites

Depending on their physical and chemical properties and the amount of replacements with cement, fly ashes may provide an economical production possibility in concrete industry and improve the mechanical and durability performance of concrete. In recent years, ultrafine fly ash has become one of the necessary ingredients of high-performance concrete. However, many of the fly ashes are coarse in nature, hence grinding is necessary to obtain sufficient performance in concrete production. In this study, the effect of grinding on strength activity of ground high-calcium fly ashes was investigated. Physical characteristics such as sieve fineness, grain particle size characteristics and Blaine specific surface area were also determined and compared with raw fly ash. Some case studies and possible interactions between fineness of fly ash, strength and water demand of mortars were discussed. The optimization of fineness coupled with the adjustment of water content were found as the key parameters of effective utilization of high-calcium fly ashes from the view point of strength maximization of cement mortars.     

减水剂在粉煤灰水泥浆体中的吸附及其流变性能影响

针对减水剂—粉煤灰体系的相互作用与分散特性开展研究,通过采用不同性质的粉煤灰和减水剂,研究了减水剂在水泥等胶凝颗粒上的吸附量、zeta电位等界面化学性质,并且测定了不同系统的屈服应力和塑性黏度等流变特性,建立了减水剂吸附量、zeta电位和水泥浆体流变参数之间的关系。试验结果表明:高效减水剂在粉煤灰颗粒表面的吸附规律与水泥颗粒完全不同。由于粉煤灰颗粒较为光滑并且表面动电位为负值,因此对高效减水剂的吸附能力较弱,其吸附能力随粉煤灰密度和颗粒大小差异较大。对于粉煤灰水泥浆体,其流变参数变化与减水剂吸附量关系较小,主要受粉煤灰技术性质的影响。由于粉煤灰表面动电位绝对值远高于掺入减水剂的硅酸盐水泥颗粒表面动电位绝对值,因此其自身具有颗粒分散趋势,及粉煤灰颗粒自身具有增加水泥浆体流动能力的能力。硅酸盐水泥和粉煤灰颗粒吸附萘系减水剂的能力大于吸附聚羧酸盐减水剂的能力。     

Assessment of phase formation in alkali activated low and high calcium fly ashes in building materials

The alkali activation of one low calcium hard coal fly ash and four high calcium lignite coal fly ashes was studied by means of conduction calorimetry, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy to assess their potential for mortar and concrete production. The ashes were activated by different additions of sodium silicate with a molar SiO₂/Na₂O ratio of 1.0. Besides the chemical analysis of the hydrated samples, strength tests have been carried out on mortars, applying different curing regimes. The results indicate that a high content of vitreous phase and low calcium content are important factors determining the reactivity and performance of fly ashes in alkali activated systems. In the high calcium fly ashes, less alkali aluminate silicate hydrates and a much more porous microstructure are formed compared to the low calcium fly ash. Consequently, the low calcium fly ash seems to be suited best for the production of building materials.     

粉煤灰-钛白石膏路基材料的研究

研究了不同的激发剂掺量对钛白石膏-粉煤灰复合材料的强度和自由线膨胀率等性能的影响,以及减水剂的作用,复合材料的耐水性和抗硫酸盐侵蚀性能等．选用三种不同类别粉煤灰与钛白石膏进行复合．试验结果表明,原状粉煤灰与高钙粉煤灰混合后再与钛白石膏复合的材料。比两种灰单独掺加时效果更好．所研制的复合材料具有较好的力学性能和优异的抗硫酸盐侵蚀性能。     

取消保温层后灰库仓壁环向内力的实例分析

本文为增加施工便利,取消了灰库仓壁保温层,并针对取消保温层后的灰库仓壁,分析了在贮料压力及温度作用下的仓壁环向内力,得出灰库仓壁环向为偏心受拉构件的结论。经过计算,重新调整仓壁厚度及配筋可以满足设计要求,取消保温层是可行的。     

Influence of fly ash fineness on the chloride penetration of concrete

In this paper, the resistance to chloride penetration of concrete containing fly ash of various finenesses was examined. Three different fly ash finenesses viz., original fly ash, 45% fine portion and 10% fine portion fly ashes were used for the study. Chloride resistance of concretes was evaluated using the measurement of the Coulomb charge as per ASTM C1202 and by determination of chloride ingress after different periods of exposure to 3% NaCl solution in full immersion and partial immersion modes. From the tests, it is found that the resistance to chloride penetration of concrete depends on the fineness of fly ash. The rapid chloride permeability test (ASTM C1202) clearly indicates that the Coulomb charge of concrete at the age of 28 days is significantly reduced with the incorporation of fly ash. The decrease is promoted with an increase in fly ash fineness. The immersion of cut cylinders in the 3% NaCl solution for 3 and 6 months confirm that the resistance of the chloride penetration of concrete increases with an incorporation with fly ash and with an increase in the fly ash fineness.     

掺土粉煤灰在坝基路基中的特性研究

粉煤友是火电厂燃煤的副产品,如何处理利用粉煤灰是国内外十分关注的问题。目前解决这一问题的途径很多,利用粉煤灰作为坝基、路基等填筑材料是比较有效的消纳方法。粉煤灰在许多方面具有比较优越的工程性能,但因为纯粉煤灰缺少必要的粘聚力．在动力作用下易发生动强度急剧降低并产生液化现象,从而对工程的安全运行造成不利影响。在粉煤灰中掺合不同量的黏土有望改善粉煤灰的工程性能。