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用有限元模拟拱坝坝体、非连续接触单元模拟坝肩,计算了在设计地震荷载作用下小湾拱坝坝肩残余位移和坝体应力。以拉应力达到坝体混凝土抗拉强度为控制标准,得出坝肩岩体的动力稳定安全系数。计算结果表明,小湾拱坝坝肩仍具有一定的安全度。 相似文献
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基于动接触力法的拱坝坝肩抗震稳定有限元分析 总被引:8,自引:2,他引:6
本文提出了应用基于动接触力方法的显式有限元技术进行拱坝坝肩抗震稳定分析的新思路,给出了相关公式。新的分析方法,将坝肩岩体、地基、坝体和库水作为一个统一体系进行动力分析计算,能有效地考虑坝肩可能滑动块体与坝体的动力相互作用,较真实地反映拱坝和坝肩受到地震作用的实际状态,并对小湾拱坝坝肩震稳定进行了分析研究。结果表明:在设计正常水位情况,小湾拱坝的地震作用超载安全系数约为1.3;在设计地震作用下,小湾拱坝的“降强安全系数”仅为2.58,而仅考虑静载作用时,即使以拱坝坝端应力不超过静态抗拉强度作为达到极限状态的工程判别定量标准,其坝肩的静态“降强安全系数”也高达4.0以上。因此,地震的作用使安全系数有较大降低。小湾拱坝坝肩抗震稳定是安全的,但安全裕度不高。 相似文献
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拱坝有缝坝体-坝基系统的非线性抗震分析 总被引:6,自引:0,他引:6
本文将坝体和坝肩裂隙岩体作为允许局部开裂和大变形的非线性连续体,用动态接触单元模型进行概化模拟,对小湾高拱坝坝体-坝基系统在高水位运行期遇设计地震荷载作用时的动力反应进行了非线性数值计算,研究了横缝对坝体应力、变形的影响,并对坝肩裂隙岩体的抗震稳定进行了分析评价,数值分析表明:横缝对拱坝坝体的应力和变形影响显著,坝肩潜在滑面的开裂和滑移导致坝体应力增大,坝体的抗震安全性降低,但在运行期高水位遇设计地震荷载时坝体和坝肩裂隙岩体整体稳定。 相似文献
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合理的拱坝布置方案是在满足枢纽布置,建筑物运用和坝肩基岩稳定的需求下,通过调整其外形尺寸,使坝体材料强度得到充分发挥,应力满足规范要求,且坝体工程量较少。作者以大潭水电站拱坝设计实例,阐述了拱坝的布置和应力分析及坝肩岩体稳定分析。 相似文献
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小湾拱坝坝肩岩体稳定分析 总被引:2,自引:0,他引:2
根据小湾坝址区断层及节理裂隙等结构面的分布状态,分析了坝肩岩体潜在的滑移边界,并作了最不利产状的分析确定.通过多种滑移型式及荷载组合分析,明确了小湾拱坝坝肩岩体的控制滑移型式及荷载工况.此外,在坝肩岩体稳定分析中,还进行了渗透压力及岩体抗剪强度指标的浮值分析,明确了影响小湾坝肩岩体稳定的主要控制因素. 相似文献
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合理的拱坝布置方案是在满足枢纽布置、建筑物运用和坝肩基岩稳定的需求下,通过调整其外形尺寸,使坝体材料强度得到充分发挥,应力满足规范要求,且坝体工程量较少。文章以新坑水库砌石双曲拱坝设计实例,对拱坝的布置和应力及坝肩岩体稳定进行了分析。 相似文献
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孟底沟水电站高拱坝由于左岸坝肩岩体受到 f1、f2、f6断层的切割,使得左坝肩形成了四个大块体。由于 f6与库水连通,若不做处理,蓄水后作用在 f6上的全水头渗压势必将使左岸坝肩岩体向河谷变形。因此左坝肩岩体变形连续性,拱坝坝体变位对称性及坝肩控制性滑块稳定性成为该工程的突出问题。充分考虑左岸坝肩断层交汇和切割关系,采用刚体弹簧元法对上述问题进行了计算分析和研究。结果表明:f6断层水压推力作用将使得断层交汇处出现不连续变形,断层产生错动现象,断层交汇点最大错动位移达到2.03 cm ,同时削弱了拱坝坝体变位对称性,左右半拱顺河向和横河向最大位移差分别为1.42 cm 和0.86 cm ;坝肩控制性滑移块体稳定安全系数下降,最大降幅可达18.19%。建议对 f6进行封堵或者置换处理,防止库水侵入山体。 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