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文章介绍了兴头水库工程混凝土试块质量评定过程,对不同组数的砌体工程用砂浆和混凝土抗压强度、普通混凝土工程用混凝土抗压强度、支护工程用喷射混凝土抗压强度以及道路工程用路面混凝土弯拉强度按不同方法进行统计分析和质量评定,可为其他类似工程的混凝土试块质量评定提供借鉴和参考。 相似文献
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为了研究不同浓度硫酸盐以及腐蚀时间对混凝土力学性能的影响,在不同浓度硫酸盐溶液中对混凝土进行腐蚀,对不同腐蚀时间的混凝土进行单轴抗压试验,研究了硫酸盐腐蚀过程中,混凝土抗压强度的变化,结果表明:在同一浓度硫酸盐溶液腐蚀过程中,随腐蚀时间增加,混凝土单轴抗压强度先增加后减少;在腐蚀前期,硫酸盐浓度越高,混凝土强度越高;在腐蚀后期,硫酸盐浓度越低,强度越高。 相似文献
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文章对水库堤坝地下水类型及其富水性、地下水的补给与排泄、地下水水位、地下水的腐蚀性、土中易溶盐腐蚀性等水文地质条件进行了抽水试验;并对场地地震效应与抗震设防标准进行了评价。结果显示,地下水对混凝土结构为弱腐蚀,对钢筋混凝土结构中的钢筋为微腐蚀,土壤对钢结构为微腐蚀。场地虽属抗震不利地段,但重新构筑钢筋混凝土护岸后,不会构成稳定性问题。 相似文献
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堆石混凝土技术是基于自密实混凝土技术发展起来的一种新型大体积混凝土施工技术,其块石料源通常具有一定的不确定性,故对其进行现场试验是该技术成功应用的重要保证。本文论述了浯溪口水利枢纽工程中分别采用基础开挖岩石和当地鹅卵石作为堆石体浇筑大型堆石混凝土试块,并对其进行强度、渗透和碳化等特性试验和温升监测过程。通过试块的浇筑质量及抗压强度、渗透系数、弹性模量、碳化深度和内部温升等多项指标对比分析了两种堆石混凝土试块特性,并论证了将开挖岩石作为堆石混凝土堆石料的可行性。 相似文献
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文章对于水利水电工程普通混凝土抗压强度统计分析进行了研究,阐述了普通混凝土试块取样及质量评定统计分析要点;对于采用普通混凝土试块抗压强度评定计算表进行快速准确统计分析进行了填表使用介绍。 相似文献
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混凝土结构在盐碱溶液侵蚀下出现裂缝,随之渗入的盐溶液使结构耐久性降低导致经济损失巨大。针对新疆阿克苏地区排渠盐碱溶液对混凝土桥墩、闸墩、涵洞等建筑物的侵蚀破坏现状,在养护室内制备标准混凝土试块,根据阿克苏周边若干排渠水样主要氯盐的含量组分,配置了不同的盐溶液,在室内对混凝土试块进行模拟侵蚀破坏试验,对其抗压强度、抗渗性进行周期监测。试验分析表明,阿克苏地区盐碱排渠对混凝土结构的侵蚀破坏比较严重,存在较大安全事故隐患。盐碱溶液液面以下混凝土结构氯离子含量最大,无较大侵蚀破坏现象;位于水位变动区的混凝土试块氯离子平均含量次之,但破坏最为严重。 相似文献
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腐蚀性地下水对水利水电工程混凝土结构的耐久性和可靠性影响很大,为预防和处理腐蚀性地下水对工程结构的不利影响,必须深入了解混凝土结构和钢筋结构腐蚀机理,文章以和田河大型灌区和田县2017年骨干工程节水改造一期工程为例,对腐蚀性地下水影响工程结构的机理和预防处理措施加以探讨。 相似文献
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文中选取三种不同强度等级配合比进行试验研究,根据工程部位的需求,进行配合比设计,试块的成型及强度测试,最终得出符合工程需要的合理配合比,主要研究分析混凝土试件的抗压强度、劈拉强度。结果表明:随着龄期的增长抗压强度和劈裂强度增强;强度等级要求高的混凝土,其抗压强度和劈裂强度测试值也高;28 d的测试强度均满足强度要求。 相似文献
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根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。 相似文献
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The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects. 相似文献
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In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment. 相似文献
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V. K. Konovalov O. V. Yashkin V. V. Ermakov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2008,42(2):105-109
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed
in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash
and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers
of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional
components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect
dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system,
configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants
of dry ash utilization and the advantages of producing of size-separated particles are considered.
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Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008). 相似文献
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Peter B. Bayley 《河流研究与利用》1991,6(2):75-86
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed. 相似文献
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简述天湖水电站投运以来各种故障的表现形式,分析其原因,提出了相应的处理方法及措施,并对合理利用国内外设备提出建议。 相似文献