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文章介绍了龙羊峡水电站码头工程中聚丙烯纤维喷射混凝土的应用,分别对掺入聚丙烯纤维的喷射混凝土和未掺入聚丙烯纤维的喷射混凝土的抗压强度、劈拉强度、抗渗性能、干缩性能、回弹量等性能进行了对比,说明了掺入聚丙烯纤维对改善和提高喷射混凝土性能的作用。 相似文献
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秦鸿飞 《河南水利与南水北调》2013,(13):66-67
开展普通引气粉煤灰混凝土、掺加聚丙烯纤维和纤维素纤维引气粉煤灰混凝土的早期开裂性能及力学性能对比试验研究。试验结果表明:掺入聚丙烯纤维、纤维素纤维可不同程度的改善混凝土早期抗裂性能,掺加聚丙烯纤维的早期抗裂效果优于纤维素纤维;掺入纤维素纤维使混凝土立方体抗压强度有显著的提高,而掺加聚丙烯纤维对混凝土的影响并不显著且略微下降;掺加纤维素纤维对混凝土的抗折强度有明显的改善,而掺加聚丙烯纤维对混凝土抗折强度没有太大的影响且略微下降。 相似文献
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聚丙烯纤维混凝土的试验研究 总被引:6,自引:0,他引:6
本文根据对聚丙烯纤维混凝土的试验研究,提出了几种聚丙烯纤维掺入混凝土使其各项技术指标改善的作用机理并采用了有关实验数据。供工程技术人员参考。 相似文献
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聚丙烯纤维对混凝土抗裂性能的影响 总被引:12,自引:0,他引:12
对聚丙烯纤维混凝土的力学性能、变形性能、抗裂性能及耐久性能进行了试验研究。结果表明:在混凝土中掺入一定量的聚丙烯纤维是克服混凝土开裂的有效途径。纤维在混凝土中所形成的乱向支撑体系,产生一种有效的二级加强效果,能较大幅度地提高混凝土的抗裂性能,改善混凝土的抗渗性能。本文同时探讨了聚丙烯纤维对混凝土抗裂性能影响的机理。 相似文献
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矿渣聚丙烯纤维混凝土抗劈拉性能试验研究 总被引:1,自引:1,他引:0
聚丙烯纤维和磨细粒化高炉矿渣对混凝土抗劈拉性能有一定程度的影响,为此,有必要研究聚丙烯纤维和矿渣的掺入量及其对混凝土抗劈拉性能的作用机理。将不同掺入量的聚丙烯纤维和不同含量的磨细粒化高炉矿渣掺入混凝土中,制成63个100 mm×200 mm的圆柱体试样,按照ASTMC496-04标准进行抗劈拉试验,并通过SEM对微观结构进行观测。研究表明,掺入不超过0.6%的聚丙烯纤维的混凝土其抗劈拉强度较大,当矿渣替代水泥不超过55%时,抗劈拉强度比不掺矿渣的试样高,SEM照片从微观结构方面揭示了强化作用机理。适量聚丙烯纤维的掺入提高了混凝土抗劈拉强度,适量矿渣的掺入也提高了混凝土抗劈拉强度,聚丙烯纤维和矿渣复合效应显著。 相似文献
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通过平板法试验,研究了采用人工中砂、人工粗砂、天然砂,以及掺入聚丙烯纤维时,对混凝土早期开裂的影响。试验结果表明,采用天然砂代替人工砂或在人工砂中掺入聚丙烯纤维,均可以有效抑制混凝土早期裂缝的产生,提高混凝土抵抗早期开裂的能力。 相似文献
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陈倩 《水利与建筑工程学报》2019,(6):113-116
向超高性能混凝土中掺入适量粗骨料,可在不降低其力学性能的前提下有效减少胶凝材料的用量,降低其成本。同时,为改善混凝土固有的抗拉强度低的缺陷,将聚丙烯纤维和钢纤维混杂掺入混凝土中可取得较好成果。考虑聚丙烯纤维体积掺量和长径比、粗骨料掺量3个因素,设计并制作了18组共54个超高性能混凝土试块,通过试验研究分析聚丙烯纤维特征参数和粗骨料掺量对含粗骨料超高性能混凝土劈裂抗拉强度的影响规律。结果表明,试验参数范围内,随着聚丙烯纤维体积掺量的增加,UHPC的劈裂抗拉强度呈现先减后增再减的规律;随着聚丙烯纤维长径比的增大,呈现先减后增的规律;聚丙烯纤维最佳配比为体积掺量0.10%,长径比167;掺入质量分数为15%的粗骨料不会降低UHPC的劈裂抗拉强度,但当粗骨料掺量提高到30%时,UHPC的劈裂抗拉强度降低明显。 相似文献
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为研究聚丙烯纤维和磨细粒化高炉矿渣对水工混凝土抗弯性能的影响,以普通混凝土试样为对照,对聚丙烯纤维混凝土、矿渣混凝土、矿渣聚丙烯纤维混凝土试样进行了简支梁法弯折性能试验,并通过扫描电镜对试样的微观结构进行观测和分析。结果表明,掺入适量聚丙烯纤维,可抑制微裂缝的产生和扩散,延缓和抑制宏观裂缝的出现和发展,提高混凝土抗弯强度,同时还能提高持荷变形能力和混凝土吸收能量的能力以及混凝土的韧性。适量矿渣及其水化物的掺入,增加了基体微观结构的密实性,可提高混凝土抗弯强度。化学和物理分析认为,掺入0.1%~0.6%聚丙烯纤维和低于55%含量的矿渣,复合效应显著。 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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Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river. 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