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稀性泥石流冲刷规律的试验研究 总被引:3,自引:1,他引:2
稀性泥石流具有很强的输沙能力,可在运动过程中强烈刷深泥石流沟道.以理论分析和野外水槽试验相结合,对稀性泥石流的冲刷规律进行了初步的探讨研究.沟床物质的初次冲刷应该考虑非均匀床沙是否会发生粗化,因此根据沟床物质在稀性泥石流的冲刷作用下形成粗化层的临界判别条件,将稀性泥石流的冲刷归纳成3种不同的模式,并分别推导了这3种不同冲刷条件下,床面冲刷深度的计算方法.然后进一步通过野外水槽试验探讨了床沙全沙输移情况下,沟床冲刷系数的取值.稀性泥石流累次冲刷问题的关键是前一次冲刷形成的床面结构是否会破坏或再生,本文最后结合野外水槽试验中累次冲刷的试验结果,分析了沟床累次冲刷深度的计算方法. 相似文献
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为了解堆积于不同坡度沟床上的堰塞坝溃口下切过程,开展了7组不同沟床坡度(7°,8°,9°,10°,11°,12°,13°)的水槽试验。试验结果表明:堆积于不同坡度沟床上的堰塞坝在漫顶溢流破坏模式下具有相似的溃口下切过程,具体可分为3个阶段,即溃口贯通阶段、加速侵蚀阶段、减速侵蚀阶段。不同沟床坡度条件在一定程度上影响溃决的加速侵蚀阶段,当沟床坡度≥9°时,加速侵蚀阶段以下切侵蚀为主、溯源侵蚀为辅的特征现象被削弱;溃决历时与沟床坡度呈非单调关系,随沟床坡度的增加呈现出先减少后增加的变化趋势;平均下切侵蚀和溯源侵蚀率与沟床坡度呈非单调关系,随沟床坡度的增加呈现出先增加后减小的变化趋势。沟床坡度缓于11°时,溃决历时对沟床坡度的敏感性高于坝前库容;沟床坡度陡于11°时,溃决历时对沟床坡度的敏感性低于坝前库容。 相似文献
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小秦岭地区的地形地貌、气象与水文、岩土体性质以及人类活动等,使该区成为泥石流多发区。该区域泥石流发生的环境条件因子有:流域内单位面积松散固体物质数量、地质构造、补给形式、补给位置、流域面积、植被覆盖、山坡平均坡度、流域形态、沟床平均比降等。通过对影响因子的量化权重标准进行分析与计算,认为小秦岭地区大部分山谷都处在泥石流旺盛发育阶段。 相似文献
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泥石流龙头运动的实验研究及能量理论 总被引:10,自引:4,他引:6
本文采用多种卵石进行水流冲刷沟床沉积物发展形成两相泥石流的实验,研究了泥石流的形成和发展过程,发现了形成泥石流的临界坡降与沟床卵石粒径的关系,揭示泥石流头部隆起高度与龙头卵石粒径成正比,提出了小卵石瞬时速度高而大卵石平均速度高的碰撞分选机理。本文建立了龙头运动的能量理论和泥石流平均速度的理论公式,并成功地计算了泥石流运动的平均速度。 相似文献
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为了研究人工填筑黏性土起动和冲刷特性,采用资料分析和试验相结合的方法,研究人工填筑黏性土的起动冲刷特性。根据试验资料,结合力学特性确定影响人工填筑黏性土起动冲刷的主要因素;根据试验结果分析人工填筑黏性土起动切应力、冲刷率分别与各自的影响因素之间的对应关系,提出了量纲和谐的起动切应力和冲刷率的公式,运用多元线性回归方法确定了公式中的系数和指数,并分析比较了人工填筑黏性土和黏性泥沙起动和冲刷特性。结果表明:人工填筑黏性土的黏结力比自然淤积固结的黏性泥沙大得多,较难起动和冲刷,需要较大的水流切应力;干密度对自然淤积黏性泥沙冲刷率影响比对人工填筑黏性土要大。 相似文献
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洪水侵蚀沟床形成泥石流是泥石流的主要类型之一,研究其形成机理和形成的临界条件有助于泥石流治理和预警预报。借鉴河流动力学中推移质输沙理论,对已有洪水侵蚀沟床形成泥石流的水槽试验资料分析表明,洪水侵蚀沟床所形成泥石流的体积输沙浓度随沟床固体颗粒物质无量纲切应力的增大而增大,且呈幂函数关系。采用定量标准作为泥石流形成判别条件,则泥石流形成临界条件是体积输沙浓度计算公式的一个特例,此时床面颗粒无量纲切应力为0.655,远大于泥沙颗粒起动无量纲切应力。基于10组水槽试验资料和1组蒋家沟原型观测资料的适用性分析表明,建立的体积输沙浓度计算公式是合理的,能够反映泥石流形成和输移规律,可用于指导泥石流形成临界水力条件的计算。 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