共查询到20条相似文献,搜索用时 62 毫秒
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澶у瀷鏂滈潰鍓垏浠殑鐮斿埗鍜岃瘯楠� />
鏂藉缓鍕� 閽卞寰� 鏈变繚鍧� />鏍囧噯鐮�榛忓湡 HDPE鍦熷伐鑶滀笌榛忓湡鐣岄潰 澶т綅绉诲己搴� 《人民长江》2013,47(6):754-761
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声波法在测定地下洞室围岩松弛带中的应用 总被引:3,自引:0,他引:3
简述声波法测定地下洞室围岩松弛带的原理和方法,以百色水利枢纽工程为例,介绍地下洞室开挖过程中采用声波法测定洞室围岩不同的波速层,从而划定围岩松弛带的范围与形状的方法.实践证明,声波法快速测定地下洞室围岩松弛带,是地下洞室开挖推广新奥法施工不可缺少的现场监测手段. 相似文献
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楞古水电站前期勘查发现自然边坡存在岩体大范围松动现象,主要表现为岩体结构面普遍张开、碎裂化程度高、围岩应力低、自稳性差。针对这一特殊的岩体结构,对岩体的松动类型和变形破坏特征进行了研究。通过对边坡岩体进行详细的地质编录和物理勘探试验,重点对节理裂隙的空间发育规律、碎裂结构岩体的空间分布及边坡已有变形破坏模式等方面进行了详细研究,同时结合声波测速、电磁勘探等试验成果,划分了岩体松动类型,归纳了每一种主控因素下的岩体变形破坏特征及破裂松动的演化过程。结果表明:岩体松动类型可划分为卸荷控制型、断层控制型、倾倒控制型以及节理裂隙控制型等4种类型,岩体的松动受浅表生改造和构造活动影响较大,节理化结构加剧了破裂过程。研究成果丰富了已有分类体系,对评价边坡稳定性以及控制地下工程围岩稳定和保障施工安全具有重要指导意义。 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