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1.
以推求城市最优暴雨强度公式为目的,选取某市以年最大值法选样10个历时的30年降雨资料,分别采用皮尔逊Ⅲ型分布曲线、耿贝尔分布曲线和指数分布曲线对其进行理论频率分析。确定"重现期-暴雨强度-降雨历时"的关系,通过采用高斯-牛顿、遗传算法和拟牛顿算法分别推求单一重现期暴雨强度公式、规范型总公式和变参型总公式。按照"公式编制精度以满足规范为前提,兼顾型式统一、应用方便"的原则,根据推求暴雨强度公式过程的误差结果分析,推荐使用由指数高斯-牛顿拟合的规范型总公式。  相似文献   

2.
根据扬州市主城区雨量站27年(1985~2011)的暴雨整编资料,采取年最大值法建立数理统计样本,采用皮尔逊-Ⅲ型频率曲线对所选样本进行拟合,得出暴雨强度i-降雨历时t-重现期p的关系,根据此关系表,运用SPSS统计软件计算暴雨强度公式各参数并进行精度分析,从而得到扬州市各重现期的暴雨强度分公式及暴雨强度总公式。结果表明:该方法拟合精度高,适用于其他同类型城市暴雨强度公式的编制。  相似文献   

3.
利用自动雨量计记录资料来编制城市雨水沟道设计暴雨强度公式的工作可以分为前、后两部分,前半部分是从降雨曲线资料得出一个降雨强度——降雨历时——重现期的关系表,即i-t-P表,后半部分是从i-t-P表编制出暴雨强度公式,也就是为i-t-P表中的经验数字选配经验公式(经验曲线),在数学上属于曲线拟合问题。本文仅涉及编制公式后半  相似文献   

4.
暴雨强度公式的精度与资料的代表性有关,研究基于1983~2013年降雨资料,分析并推求出六盘水市新版暴雨强度公式。同时,新旧公式对比表明,两代公式差异显著,差率绝对值小于10%的比例仅为31.8%,大于30%的比例则占到25.0%。当降雨历时、重现期较小时,原公式暴雨强度计算值较小,反之则新公式计算值较小。  相似文献   

5.
基于历史降雨资料,采用数理分析方法,获得城市暴雨特征的量化表达,是城市风险管控、基础设施规划设计的关键性基础工作之一。根据宜昌城区短历时暴雨观测资料,应用遗传算法分别对皮尔逊-Ⅲ型频率分布曲线和暴雨强度公式参数进行了优化求解,通过趋势分析得到了近30 a的年际变化特征,采用芝加哥法分析确定了短历时暴雨雨型。结果表明:确定的宜昌城区暴雨强度满足精度要求;宜昌城区近30 a短历时暴雨的雨量峰值趋于增加,暴雨发生的历时主要集中在3 h以内。采用芝加哥法确定了重现期为2 a各降雨历时(步长取5 min)的设计暴雨雨型,雨峰位置的降雨强度随降雨历时的增加呈现出一定的上下波动,但各历时峰值在数值上相差并不明显。研究成果可为城市雨水径流控制等提供参考。  相似文献   

6.
利用昆山市1980年~2015年连续36年的降水观测资料获得降水统计样本;采用"年最大值法"进行资料选样,按照P-Ⅲ分布曲线拟合得到雨强-重现期-历时(i-P-t)三联表,根据误差最小原则确定最优方法,得到昆山市暴雨强度公式。结果表明:皮尔逊Ⅲ型分布函数各降水历时下平均相对均方差误差满足规范要求;新修订公式的暴雨强度比原公式的暴雨强度小,是目前较为合适的暴雨强度公式计算方法,可为昆山市城市建筑规划设计提供依据和参考。  相似文献   

7.
PMP—可能最大降水概念简介   总被引:1,自引:1,他引:0  
刘鹏  郭汝艳 《给水排水》2004,30(8):87-89
可能最大降水 (PMP)是指在现代气候条件及地理条件下设计地区 (或流域 )一定历时内 ,物理上可能发生的近似上限降水 ,包括降水总量及其时空分布。当今雨量预测广泛采用的方法主要有频率分析法和水文气象分析法。建筑给排水设计中常常采用的暴雨强度公式即来自频率分析法。但当重现期足够大时 ,通过分析暴雨强度公式的推求原理 ,可知在理论基础和具体技术两方面都存在一定的问题 ,其计算结果可能不可靠。国家体育场屋面雨水排水系统管道不仅要能排除长降雨历时的降雨 ,还要能排除短时间大强度的降雨 ,PMP能帮助界定降雨重现期取值的上限  相似文献   

8.
基于西安市1961~2011年共51年分钟自记雨量资料,以5a为间隔分段统计了各段年均降雨量及降雨日数、大雨量及大雨日数、暴雨量及暴雨日数和设计降雨强度,运用Mann-Kendall突变分析法和线性趋势法分析了西安市降雨模式变化。结果表明自2005年后年均降雨量和降雨日数均减少,降雨日数减少幅度更大,而大雨和暴雨日数及其雨量均增加,雨量增加幅度更大,表明降雨、大到暴雨集中度增加,2005年以后大雨和暴雨发生频次更高;同一强度降雨的重现期在2005年后较小,同一重现期的降雨在2005年后雨强更大,在2005~2009年段在重现期为1~5a的降雨中各历时强度均达到最大,结合气候变化及城市化分析了西安市降雨模式变化的原因;讨论了在气候变化和降雨模式变化条件下,以降雨历史资料为基础推求降雨强度公式,设计雨水排水系统存在的问题及与城市内涝之间的关系。  相似文献   

9.
在编制暴雨强度公式时,存在原始降雨资料中包含的异常值影响暴雨强度公式的准确度,皮尔逊-Ⅲ型理论频率曲线拟合工作量大等问题。针对以上问题,阐述了异常值剔除的方法,分析了变异系数(Cv)、偏态系数(Cs)对皮尔逊-Ⅲ型分布曲线拟合的影响规律。同时,基于重庆市酉阳县1993-2013年共计21a的暴雨资料,采用Excel规划求解优化皮尔逊-Ⅲ型分布曲线的拟合参数,分别利用基于规划求解的最小二乘法和高斯牛顿法,推求暴雨强度公式,并对其拟合精度和误差进行了对比分析。提出的规划求解法能有效避免拟合暴雨强度公式适线过程中目估适线法所导致的主观影响,通过对比分析解析了提高收敛速度和精度的暴雨强度总公式的推求方法。  相似文献   

10.
降雨资料的选样是暴雨强度公式编制的基础,目前常用的方法为年最大值法和年多个样法。阐述了两种方法推求公式的优劣,并利用江苏淮安市计算实例建立了两者重现期之间的转换关系。依据城市发展及降雨资料情况,建议推广年最大值法,并编制了两种取样方法的暴雨强度公式,用以解决工程设计中两种方法使用时的衔接问题。  相似文献   

11.
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   

12.
The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L?1, the median total phosphorus was 0.29 mg L?1 and the median total nitrogen was 1.56 mg L?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.  相似文献   

13.
Call for Papers     
正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.  相似文献   

14.
Carbon dioxide (CO2) and methane (CH4) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO2 and CH4 diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 106 t CO2eq km2 per year, or 24 × 106 t CO2eq per year. This corresponds to a plant emission factor of 3.18 kg CO2eq MWh?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO2eq per year, or 5.83 kg CO2eq MWh?1, which is in the lower range of the studied reservoirs.  相似文献   

15.
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   

16.
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. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).  相似文献   

17.
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   

18.
为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。  相似文献   

19.
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   

20.
岩石动态拉伸断裂特性的实验研究   总被引:1,自引:0,他引:1  
采用新近发展起来的拉伸式Hopkinson冲击装置(SHTB),对岩石切口圆柱断裂试样进行了动态拉伸断裂特性的实验研究。同时,利用MTS试验机进行了岩石的静态拉伸断裂实验,成功地获得了岩石试样的断裂韧度及断裂能随加载率而变化的实验结果。对静态和动态破坏后的试样断口进行的扫描电镜观察进一步表明,试样断口形貌的复杂程度与其断裂耗能有着十分密切的联系。  相似文献   

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