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21.
特大型桥梁工程地质勘察区域地壳稳定性研究 总被引:1,自引:0,他引:1
重大工程区域地壳稳定性研究,是工程前期工程地质勘察的重要内容之一,并越来越多地为工程建设所重视。大桥工程地质勘察以往对此涉及较少,也无明确的统一规定,以长江上所建特大桥为例,对此项工程作了些探索性的研究,重点研究的问题是:区域构造环境及构造变形,地壳结构和深部构造,新构造活动,断裂活动,地震活动等,为大桥建设宏观决策和抗震设计提供依据。 相似文献
22.
一级开发大柳树高坝原始库容比二级开发小观音高坝多 4 0亿m3 ,库容大带来的好处体现在 5~ 7月可多向下游增供水量 ,缓解下游河道断流 ;延长泄放清水时间 ;增加发电效益 ;满足宁蒙河段防凌要求 ;增加汛期集中泄水 ,减缓下游河道淤积萎缩 ;满足南水北调西线工程水量调节要求等。为了更好优化配置黄河水资源 ,从全局和长远利益考虑 ,应采用一级开发方案 ,修建大柳树高坝大库 相似文献
23.
高晓梅 《水利水电工程设计》2002,21(4):1-4
永定新河是天津市防洪的北部防线。由于受海相来沙淤积 ,河道行洪能力大幅度下降。针对永定新河治理工程设计中涉及到的河道淤积治理方案、闸位比选、防潮闸结构型式及施工方法、闸下减淤清淤措施等诸多问题进行了分析和研究 ,提出了相应的措施和建议 相似文献
24.
Modelling the effects of dam removal on migratory walleye (Sander vitreus) early life‐history stages
Many dams in the USA have outlived their intended purpose and an increasing number are being considered for removal. Yet, quantitative studies of the potential physical, biological and ecological responses are needed to assess dam removal decisions. In this paper, the responses of migratory walleye (Sander vitreus) to increased spawning habitat availability as a result of dam removal was studied by comparing scenarios with and without a high‐head dam in the Sandusky River (Ohio), a major tributary to Lake Erie. A conceptual, ecological model was proposed to define the relationship between hydrodynamics and walleye spawning, egg hatching, larval drift and survival. A mathematical, ecological model of the early life‐history stages was then developed and coupled with time series of depth and velocity predictions over the spawning grounds from a 1‐D hydrodynamic model. Model simulations were run for 1984–1993 for both the with‐ and without‐dam scenarios to assess the potential benefit of dam removal. The simulation results demonstrated that velocity, depth and water temperature are major factors influencing adult walleye spawning success. Without the dam, 10 times the amount of spawning habitat would be available for walleye to spawn. This increase in spawning habitat area resulted in up to five times the total egg deposition and seven times the larval output to the nursing grounds, based on the assumption that 5% of the walleye population of Lake Erie migrated up the Sandusky River to spawn. We concluded that the spawning habitat in the current condition (with the dam) is limiting and additional spawning habitat upstream could significantly increase the number of larval walleye drifting to Lake Erie. The model sensitivity analysis showed that the number of walleye migrating up the river in spring is the dominant factor for larval recruitment to the lake. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
25.
There is widespread application of indicators to the assessment of environmental condition of streams. These indicators are intended for use by managers in making various comparative and absolute assessments and often have a role in resource allocation and performance assessment. Therefore, the problem of formally defining confidence in the results is important but difficult because the sampling strategies used are commonly based on a compromise between the requirements of statistical rigour and the pragmatic issues of access and resources. It is rare to see this compromise explicitly considered and consequently there is seldom quantification of the uncertainty that could affect the confidence a manager has in an indicator. In this paper, we present a method for quantitatively assessing the tradeoffs between sampling density and uncertainty in meeting various monitoring objectives. Assessments using judgement‐based representative reaches are shown to be unreliable; instead a sampling approach is recommended based on the random selection of measuring sites. A detailed dataset was collected along two streams in Victoria, Australia, and the effect of sampling density was assessed by subsampling from this dataset with precision related to the number of sites assessed per reach length and the intensity of the sampling at each site. The sampling scheme to achieve a given precision is shown to depend on the monitoring objective. In particular, three objectives were considered: (1) making a baseline assessment of current condition; (2) change detection; and (3) detection of a critical threshold in condition. Change detection is shown to be more demanding than assessing baseline condition with additional sampling effort required to achieve the same precision. Sampling to detect a critical threshold depends on nominating acceptable values of Type I and II error and the size of the effect to be detected. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
26.
胜利炼油厂重油加氢 (VRDS)装置的常压分馏塔为填料塔 ,2 0 0 1年检修开工后该系统出现异常 ,经过查找分析 ,确定轻烃 /产品减压渣油换热器和柴油汽提塔重沸器内漏是装置异常的主要原因 相似文献
27.
河口水流、波浪、潮流、泥沙、河床变形二维数学模型 总被引:19,自引:0,他引:19
根据河口“波浪掀沙,潮流输沙”的泥沙运动机制,引入“波浪幅射应力”反应波浪对水体和泥沙的驱动力.考虑波浪对底部泥沙作用力、波浪对水流挟沙能力的影响及风场对水流和泥沙运动的影响.同时考虑泥沙粒径大小、水体含盐度、含沙量及水流紊动程度等因素对絮凝沉速的影响.用ADI算法求解沿水深平均方程,破开算子法解悬移质不平衡输沙方程及河床变形方程,引入通度概念处理岸滩不规则边界,建立河口水流、波浪、潮流、泥沙、河床变形二维数学模型.通过实测资料及卫星摇感图像对所建数学模型进行检验,表明它可以较好地预测河口泥沙的运动 相似文献
28.
29.
从恒定、渐变流河段能量方程式中推导出以高程与河道断面特性平均积分曲线图解河道水面线的方法,并通过某河段水面线计算实例说明了此方法的计算图解步骤。对于同一河道,由于高程与河道断面特性平均积分曲线不变。故曲线可重复利用。因此,对进行多种设计标准的水面线计算可很方便地直接从曲线图上得出水面线结果。 相似文献
30.
简述江西省抚河流域的概况、水生态环境的现状及存在的问题.包括淤泥的堆积、水土的流失、水污染、沿岸圩堤的防洪标准普遍偏低等.并对这些问题提出了流域水生态环境恢复的目标,针对抚河流域水生态环境的恢复目标提出了水权分配、水土保持治理、水工程治理、水质治理等方面的一系列初步的措施与建议. 相似文献