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聚丙烯纤维自密实高性能混凝土的配制及性能 总被引:1,自引:0,他引:1
为提高自密实高性能混凝土的抗渗抗裂性,将聚丙烯纤维增强与自密实混凝土技术很好地结合起来,进行了聚丙烯纤维自密实高性能混凝土的配制及性能试验.试验表明:随着聚丙烯纤维掺量在一定范围内(0~1.2 kg/m3)的增加,通过调整砂率、增加胶凝材料用量、增加用水量、减小骨料最大粒径、增加高效减水剂用量等措施可以保证纤维自密实混凝土的高工作性.混凝土凝结硬化后,当聚丙烯纤维掺量较低时(0~0.9 kg/m3),它对自密实混凝土的力学性能没有明显影响;当聚丙烯纤维掺量较高(大于1.8 kg/m3)时,它对自密实混凝土的力学性能会产生不良影响.纤维增强自密实混凝土的抗渗抗裂试验表明:聚丙烯纤维掺量越大,混凝土的抗裂性越强;而抗渗性则随聚丙烯纤维掺量的增大先呈增强趋势,但当聚丙烯纤维超过一定量(1.8 kg/m3)时,混凝土的抗渗性呈下降趋势.聚丙烯纤维对混凝土性能的影响主要源于其阻裂效应和弱界面效应共同作用的结果. 相似文献
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采用CHF高分子复合离子土壤固化剂,进行了一系列的固化土对比试验,分析了水泥掺量、固化剂掺量、成型压力对固化土无侧限抗压强度及抗渗性能的影响。结果:固化剂掺量0.02%,水泥掺量为8%的固化土能满足渠道工程的要求,且较为经济。 相似文献
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粉煤灰固化土护面材料的力学及渗透性能研究 总被引:1,自引:0,他引:1
笔者研究了固化剂HAS掺量11%和15%的粉煤灰固化土的抗压、抗冻、抗渗性能,并以水泥掺量25%的水泥粉煤灰固化土为对照,证明了固化剂HAS掺量15%的粉煤灰固化土的抗压、抗渗和抗冻性能均优于水泥掺量25%的水泥粉煤灰固化土,能够满足护面材料的要求。 相似文献
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我国水利工程有很多集中在西部高海拔和低温地区,这样的条件对于工程中的混凝土就提出了更高的要求。纤维以其自身独特的优点已经在工程中应用越来越广泛,针对不同纤维掺量的混凝土进行一系列耐久性研究,期望得到最佳的纤维掺量。结果表明:不同纤维掺量对于混凝土的抗压强度影响不大,当纤维掺量为1.2 kg/m3时,抗拉强度增加最多为19.9%;纤维改性混凝土能明显的改进混凝土的抗渗性和抗冻性;当纤维掺量为1.2 kg/m3时,干缩变形最小,与未加入纤维的混凝土相比降低了29.8%。因此,纤维改性混凝土能显著的提高混凝土的耐久性,且最优掺量为1.2 kg/m3。 相似文献
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用水泥和石灰等胶结剂及激发剂构成的固化剂对上海市横沙岛东滩的疏浚土进行改良,在不同养护龄期和固化剂掺量的条件下,用自配固化剂对岛区疏浚土进行了渗透试验。分析了固化疏浚土的渗透系数与固化剂掺量、养护龄期之间的关系, 得到了疏浚土渗透系数在不同固化剂掺入比和龄期下的变化规律。结果表明:固化疏浚土的渗透系数随固化剂掺量和龄期的增加而明显变小,但在同一龄期下,当固化剂掺量继续增加时,其渗透系数变化不大。并利用电镜扫描(SEM)对不同固化剂掺量和不同龄期下的固化疏浚土的微观结构进行观测,获得了疏浚土固化前后的微观结构SEM图,结合SEM图对疏浚土固化前后的微观结构变化做了定性的对比和分析,从固化疏浚土微观结构中发现固化疏浚土中含有水化硅酸钙(C-S-H)、氢氧化钙晶体、无定形文石、钙矾石等能够填充孔隙的胶结物,并从微观上解释了固化剂固化疏浚土的固化机理。 相似文献
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聚丙烯纤维掺入U型槽混凝土中能提高混凝土的抗压强度、抗折强度、抗渗性及抗冻性;当选择聚丙烯纤维最优掺量为0.8kg/m3时,预制U型槽混凝土构件的内外压力值提高20%—30%。 相似文献
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黄拓军 《水利与建筑工程学报》2011,9(2):102-105
针对混凝土的耐久性、和易性、冻融性及抗裂性等物理性能,以聚丙烯纤维掺量、膨胀剂掺量、约束条件及不同养护条件为影响因素,进行大量对比试验.通过试验分析表明,在混凝土中掺人聚丙烯纤维能明显改善混凝土的各种物理性能,当纤维长度为19mm,掺量为0.9 kg/m3时,混凝土性能提高较为显著.并把研究成果运用于工程实践,分析表明... 相似文献
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为找出广州南沙港某油罐仓储区工程淤泥加固时固化剂的最优配比,取该工程区典型淤泥,以水泥、石灰、石膏、水玻璃和减水剂作为固化剂,对淤泥进行加固试验研究,以无侧限抗压强度来检验加固效果,找到最佳的固化剂掺量,并进行固化淤泥与原状淤泥力学性能和微观结构变化的对比研究。试验结果表明,水泥、减水剂、水玻璃、石膏和石灰掺量分别为20%,1.5%,10%,6%和16%时淤泥的固化效果最佳;影响固化土强度的5个因素中,水泥掺量影响最大,石膏掺量影响最小。相比原状土样,最优配比固化淤泥试样的渗透系数和孔隙率分别减小81.0%和59.8%,三轴不固结不排水试验的黏聚力和内摩擦角分别是原状土样的3.8和4.9倍,固化淤泥的物理力学性能得到明显改善。 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