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为研究覆盖层上复合土工膜堆石坝渗流场的影响要素,基于数值模拟,分别考虑防渗墙深度、覆盖层厚度和对应的覆盖层渗透系数3种因素对堆石坝渗透性能的影响。结果表明:(1)防渗墙深度和覆盖层厚度和渗透系数对坝体总渗流量影响最大。渗流量随防渗深度增大先缓慢减小而后急剧减小;(2)覆盖层渗透性较大时,需增大防渗墙深度才能起到较好的渗流量控制效果,如渗透系数为1×10-2cm/s时,相对防渗深度至少需要达到0.9以上,才能保证渗流量控制率大于75%;(3)覆盖层渗透系数与相对防渗深度在对数坐标上满足线性关系,提出的拟合公式可对堆石坝的渗流量控制效果进行评价。 相似文献
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防渗帷幕是堤坝中最常见的防渗处理措施,施工后完全位于地下,其施工效果受到多方面因素的影响,因此对防渗帷幕这一隐蔽性工程的灌浆效果评价则显得极为重要。本文以实际工程为例,首先利用压水试验对帷幕断面灌浆后的透水性进行评价;然后利用室内试验对坝基材料的渗透稳定性进行了评价;最后在压水试验和室内试验的基础上,结合数值模拟,分别就帷幕灌浆后的渗透性和局部贯通性缺陷对渗漏量及水力比降的影响进行了敏感性分析。研究发现,帷幕灌浆后,当渗透性低至一定程度时,帷幕渗透性的降低对大坝浸润线和水力比降的分布影响较小,但对大坝的渗漏量依然有一定的影响;当帷幕中有贯通的缺陷时,缺陷处水力比降虽较大,但坝基材料颗粒级配良好,所以不存在渗透破坏的可能性。 相似文献
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李维朝 《中国水利水电科学研究院学报》2009,(Z1)
防渗帷幕是堤坝中最常见的防渗处理措施,其施工效果受到多方面因素的影响,并且施工后完全位于地下,因此对防渗帷幕这一隐蔽性工程的灌浆效果评价则显得极为重要。本文以某实际工程为例,对帷幕灌浆效果进行了评价。文中首先利用压水试验对帷幕断面灌浆后的透水性进行评价;然后利用室内试验对坝基材料的渗透稳定性进行了评价;最后在压水试验和室内试验的基础上,结合数值模拟,分别就帷幕灌浆后的渗透性和局部贯通性缺陷对渗漏量及水力比降的影响进行了敏感性分析。研究发现,帷幕灌浆后,当渗透性低至一定程度时,帷幕渗透性的降低对大坝浸润线和水力比降的分布影响较小,但对大坝的渗漏量依然有一定的影响;当帷幕中有贯通的缺陷时,缺陷处水力比降虽较大,但坝基材料颗粒级配良好,所以不存在渗透破坏的可能性。本实例研究给帷幕灌浆效果的评价提供了有意的借鉴。 相似文献
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大坝防渗设计是为截断渗漏通道,确保水库蓄水与坝体安全,是大坝设计的重要工作之一。针对后河沟水库砂砾石地层的分布位置规律不明确、渗透系数较大、覆盖层厚度平均厚度大等坝基渗漏问题,分析垂直防渗、上游防渗铺盖、下游排水设备及盖重三种防渗形式,提出垂直防渗中的截水槽+混凝土防渗墙+灌浆帷幕的处理措施,可有效解决坝基渗漏问题。 相似文献
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《人民黄河》2019,(12)
在深厚覆盖层上修建土石坝,坝体和坝基的防渗效果直接关系大坝的安全。根据西南地区某土石坝坝址区工程地质条件,坝体采用沥青混凝土心墙防渗,深厚覆盖层采用悬挂式混凝土防渗墙方案,重点对悬挂式混凝土防渗墙深度进行了6种方案对比分析,确定防渗墙深度22 m时,大坝及坝基年渗流量和渗透比降满足要求。在此基础上,进行了多个工况的校核分析,计算结果表明,采用以沥青混凝土心墙和防渗墙为主的防渗体系,有效降低了坝体内部浸润线高度,浸润线在沥青混凝土心墙处骤降,下游坝坡内部孔隙水压力较小,最大坝高处浸润线降至排水层,下游出逸点位于下游排水体中下部,沥青混凝土心墙和混凝土防渗墙的渗透比降均小于允许值80,坝体填筑材料和天然砂砾石层的渗透比降均在允许渗透比降范围内,坝体、坝基渗流稳定,不会发生渗透破坏。 相似文献
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满拉水利枢纽工程拦河坝为土心墙堆石坝,基岩为辉绿岩,河床覆盖层由砾卵石组成,厚度21~28m。坝基砾卵石覆盖层为极强透水层,渗透系数200m/d,容许渗透比降0.20,通过方案的比较和研究,采用混凝土防渗墙防渗的方案,墙体厚度0.80m,墙体混凝土强度等级为C30,抗渗等级为W8。墙下部基岩设置帷幕灌浆。本文简要介绍满拉大坝混凝土防渗墙的设计。 相似文献
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防渗处理是土石坝设计施工中的重点和难点,关系到水库运行的安全与库容调蓄功能的正常发挥.针对松塔水电站枢纽工程坝基覆盖层存在渗透变形和主要渗漏通道,坝体左右岸存在绕坝渗漏现象,最终确定采用"坝基帷幕灌浆+库岸帷幕灌浆和高压旋喷灌浆"的防渗方案.渗流分析计算结果表明,水库各项运行指标正常,大坝渗流稳定计算均能满足规范要求,... 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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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