共查询到20条相似文献，搜索用时 781 毫秒
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《地震地质》2017,(6)
以稳态的河水动力侵蚀方程为基础,分析河道高程剖面,可以得到河道陡峭系数,从而反映区域基岩隆升速率的空间分布特征。利用传统的坡度-面积分析法计算陡峭系数时,需要对原始高程数据进行平滑、重采样和微分等一系列操作来计算坡度,这会造成信息丢失和重复引入误差。而近5a来逐渐得到推广应用的积分方法,通过直接求解河水动力侵蚀方程,将稳态的河道高程剖面变换成1条直线,直线斜率即河道陡峭系数,避免了计算坡度带来的缺点。同时,该方法用积分函数表示基岩河道高程剖面,可以将陡峭系数和其他一些地貌参数(坡度长度指数、面积高程曲线积分)联系起来,为用这些参数表示区域构造活动信息提供理论依据。此外,该方法还可用于判别分水岭迁移方向。因此,综合这些优势,积分法在分析流域地貌特征和进行构造地貌的研究中具有广阔的应用前景。 相似文献
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层状介质参数反演的混合最优化法 总被引：8，自引：4，他引：4
波动方程反演是典型的非线性反问题,本文提出了用混合最优化法反演层状介质参数。混合最优化法将广义模拟退火与局部最优化方法结合,能较好地利用两者的优点,在本文中,局部最优化算法采用线性迭代算法。通过数值结果表明反演方法的正确有效性。 相似文献
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强烈下渗条件下天然河道洪水演进模拟方法 总被引：2，自引：0，他引：2
河道洪水演进模拟是河道洪水预报与汇流计算的主要内容和关键.对于常年断流、河水与地下水长期处于脱节状态的河道,一旦行洪下渗非常强烈,渗漏量很大.不考虑河道下渗洪水演进模拟模型,无法准确模拟真实的洪水运动行为,不能用于洪水模拟预报.本文采用土壤下渗理论描述河道下渗,推导出了河道下渗流量计算公式,建立了基于霍顿下渗公式的河道下渗模拟方法;并把下渗当做单位区间出流,与基于马斯京根康吉法天然河道洪水演进模型进行耦合,构建了强烈下渗条件下天然河道洪水演进模拟模型.针对天然河道水力特性复杂特点,研究了洪水演进模型参数确定方法和波速计算方法.海河流域漳卫河水系岳城水库-蔡小庄段的典型场次洪水应用结果表明,模型能很好反映强烈下渗条件下洪水演进实际情况,具有很高模拟精度,基于土壤下渗理论的下渗量计算公式和模拟方法可以很好地模拟河道下渗过程.这一模型具有计算简便、参数确定简单、适合于洪水预报等特点,在干旱和半干旱地区河道洪水演进模拟预报与河道汇流计算中也具有一定的推广应用价值. 相似文献
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快速模拟退火地震反演 总被引：10，自引：3，他引：10
讨论了用模拟退火方法进行地震资料的参数反演，利用快速的降温方式实现模拟退火反演，从而形成了快速模拟退火算法。模拟退火反演的优点是可以突破反演过程中局部最优的限制，获得全局最优解。因此，ＳＡ方法适于解决地震反演中的非凸性目标函数的最优化问题。 相似文献
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本文利用水动力学的基本理论,结合加拿大模型的求解方法,建立了一个适合太湖流域河网特点的水动力学模型,并利用该模型对太湖的主要排水河道望虞河及其支流进行了河网水利计算。计算结果表明该模型计算方法可行,计算精较高。 相似文献
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高层建筑动力反应实测中测点的优化布置方法的研究 总被引：3，自引：0，他引：3
本文对高层建筑动力反应实测中测点的优化布置方法进行了研究，研究了几种表示测点布置是否最优的适应度函数，并且应用最优化计算方法来寻找测点最优或接近优化的布置。本文还通过一个高层建筑动态响应测试的实例，说明了具体的应用方法。实际计算表明，用本文方法布置测点所测得的结构动态响应结果有相当高的精度。 相似文献
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Xu Jiongxin 《地球表面变化过程与地形》1991,16(2):129-142
River channel pattern may be regarded as the outcome of streamflow, sediment load, and channel boundary conditions, as can the grain size distribution of bed material. It may therefore be expected that connections should exist between river channel pattern characteristics and the corresponding river bed material grain size parameters. Using data from some Chinese rivers, an attempt has been made to express these connections quantitatively by using statistical methods. The work demonstrates that the river's bed load can be related to the percentage of the traction subpopulation of the bed material shown by the probabilistic plot of grain size cumulative-frequency curve. The study has also revealed some correlations between the bed material grain size parameters of rivers and their channel geometry such as channel width-depth ratio and channel sinuosity. For instance, the higher the ratio of the traction to suspension subpopulation in bed material, the more sinuous, more shallow, and wider the river channel would be. Furthermore, a discrimination function has been given to distinguish between meandering and wandering braided rivers. If the existence of these relationships can be supported by data from more rivers in other regions, then by using them we can postdict palaeoriver channel geometry and its channel pattern character from fluvial sediment grain size parameters of the palaeoriver. This would open a new way to reconstruct the physicogeographical environment in which palaeorivers developed. 相似文献
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Most downstream hydraulic geometry exponents have been found to be very close to the classic values reported by Leopold and Maddock (1953). These have been viewed as the simplified cases to general trends because the hydraulic geometry of alluvial channels is actually the product of ‘multivariate controls’ (Richards, 1982). This paper is an attempt to develop a soundly based foundation for the explanation of the physical mechanisms of these controls. A quantitative relationship between channel shape and boundary shear distribution developed from experimental flume results is found to be applicable in some instances to alluvial channels, particularly to stable canals. On the basis of this relationship, it is shown that downstream hydraulic geometry is determined not only by flow discharge, but also by channel slope, channel average roughness and sediment composition of the channel boundary. This is strongly supported by our analysis of 529 observations from both stable canals and natural rivers in the U.S.A. and the U.K. The difference between regime relations in canals and the hydraulic geometry of rivers appears to be caused mainly by channel slope and average roughness, which can be regarded as constants only in stable canals. The close relationship between discharge and channel average roughness observed in canals is not repeated in natural channels, partly because of the variety of flow values used to define the channel-forming discharge. Furthermore, it is indicated that the effects of the sediment composition of the channel boundary on hydraulic geometry are significant and need further investigation. 相似文献
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《水文科学杂志》2013,58(2):401-408
Abstract Knowledge of peak discharge is essential for safe and economical planning and design of hydraulic structures. In India, as in most developing countries, the majority of river basins are either sparsely gauged or not gauged at all. The gauged records are also of short length (generally 15–30 years), therefore development of robust models is necessary for estimation of streamflows. Various studies reveal that flood estimation through channel geometry is an alternative method for ungauged catchments. It is appropriate for use where flow characteristics are poorly related to catchment area and other catchment characteristics. In the present study, stream geometry parameters for 42 river sites in central-south India were used; calibration equations were developed with data for 35 stations and tested on data for the remaining seven stations. The relationships developed between mean discharge and channel geometry parameters provide an alternative technique for estimation of mean annual channel discharge. 相似文献
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Prabhata K. SWAMEE 《国际泥沙研究》2000,(4)
1 INTRODUCTIONA stable channel is a stream in equilibrium that is neither silting nor scouring over a period of time.Obviously, such a stream has developed a cross sectional area of flow through natural processes ofdeposition and scour. Gilbert (Chang 1988) in 1880 was perhaps the first to recognize the role ofndnilnization processes in arriving at an equilibrium cross-section of such a stream. Langbein (1964)gave an arbitrarily formed function of various knit powers obtained by dividing … 相似文献
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CAO Shuyou This research was supported financially by the Foundation for Scholars Return from Abroad of State Educational Committee the National Natural Science Foundation of China 《国际泥沙研究》1997,(3)
I.INTRODUCTIONThehydraulicgeometryofstablenaturalriversisdeterminedbyceftaincontrolfactors.suchassizeandgradationofboundarymaterial-sorting,transportandarmoring.planformofchannel.ballkstability.amongstothers.Ageometricmodelfornonuniformboundarymaterialhasbeenproposed(Cao,1996).Theentropy-basedthresholdbankprofiletheory(CaoandKnight,1996).thenext'solutionofthestablechannelparadox,basedonShionoandKnight's(1991)solutionofthedepthmean-averagedmomentumequationatthejunctionpointsareemployedto… 相似文献
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Geomorphic response of the Jingjiang Reach to the Three Gorges Project operation 总被引：2，自引：0，他引：2 
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下载免费PDF全文 Upstream damming often causes significant downstream geomorphic adjustments. Remarkable channel changes have occurred in the Jingjiang Reach of the Middle Yangtze River, since the onset of the Three Gorges Project (TGP). Therefore, it is important to investigate the variations in different fluvial variables, for better understanding of the channel evolution characteristics as an example of the Jingjiang Reach. Recent geomorphic adjustments in the study reach have been investigated quantitatively, including variations in sediment rating curve, fluvial erosion intensity, channel deformation volume and bankfull channel geometry. These fluvial variables adjusted in varying degrees in response to the altered flow and sediment regime caused by the TGP operation. A focus of this study has been especially on variation in the bankfull channel geometry. Calculated bankfull dimensions at section‐ and reach‐scale indicate that: (i) there were significant bank‐erosion processes in local regions without bank‐protection engineering, with empirical relations being developed to reproduce the variation in bankfull widths at four typical sections; (ii) the variation in the reach‐scale channel geometry occurred mainly in the component of bankfull depth, owing to the construction of large‐scale bank‐revetment works, with the depth increasing from 13.7 m in 2002 to 15.0 m in 2014, and with an increase in the corresponding bankfull area of about 11%; and (iii) the reach‐scale bankfull channel dimensions responded to the previous 5‐year average fluvial erosion intensity during flood seasons at Zhicheng, with higher correlations for the depth and area being obtained when calibrated by the measurements in 2002–2012. Furthermore, these relations developed for the section‐ and reach‐scale bankfull channel geometry were also verified by the observed data in 2013–2014, with encouraging results being obtained. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Fractal sinuosity of stream channels 总被引：4，自引：0，他引：4
R. Scott Snow 《Pure and Applied Geophysics》1989,131(1-2):99-109
Analysis of a diverse set of twelve stream channel planforms indicates that at scales relevant to river meandering, river traces are most reasonably treated as fractal curves. The atypically high degree of channel wandering apparent at such scales is a common characteristic of all single-channel streams, while identifiable meandering appears to be only one way in which this tendency is expressed. At smaller scales of view river paths have shapes of smooth curves appropriate to Euclidian geometry, and toward larger scales a distinct change in degree of wandering marks the transition to bends that are considered to be changes in general river course rather than parts of channel pattern. This analysis method provides a natural, objective calculation of river sinuosity as well as other parameters that more completely specify channel planform. 相似文献
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A dataset of 21 study reaches in the Porter and Kowai rivers (eastern side of the South Island), and 13 study reaches in Camp Creek and adjacent catchments (western side of the South Island) was used to examine downstream hydraulic geometry of mountain streams in New Zealand. Streams in the eastern and western regions both exhibit well-developed downstream hydraulic geometry, as indicated by strong correlations between channel top width, bankfull depth, mean velocity, and bankfull discharge. Exponents for the hydraulic geometry relations are similar to average values for rivers worldwide. Factors such as colluvial sediment input to the channels, colluvial processes along the channels, tectonic uplift, and discontinuous bedrock exposure along the channels might be expected to complicate adjustment of channel geometry to downstream increases in discharge. The presence of well-developed downstream hydraulic geometry relations despite these complicating factors is interpreted to indicate that the ratio of hydraulic driving forces to substrate resisting forces is sufficiently large to permit channel adjustment to relatively frequent discharges. 相似文献
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Using a dataset of gauged river discharges taken from sites in England and Wales, linear multilevel models (also known as mixed effects models) were applied to quantify the variability in discharge and the discharge‐hydraulic geometry relationships across three nested spatial scales. A jackknifing procedure was used to test the ability of the multilevel models to predict hydraulic geometry, and therefore width, mean depth and mean velocity, at ungauged stations. These models provide a framework for making predictions of hydraulic geometry parameters, with associated levels of uncertainty, using different levels of data availability. Results indicate that as one travels downstream along a river there is greater variability in hydraulic geometry than is the case between rivers of similar sizes. This indicates that hydraulic geometry (and therefore hydrology) is driven by catchment area, to a greater extent than by natural geomorphological variations in the streamwise direction at the mesoscale, but these geomorphological variations can still have a major impact on channel structure. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Atahebson B. Santos Milton J. Porsani Manuelle S. Góis 《Geophysical Prospecting》2019,67(7):1720-1731
The determination of three-dimensional geometry and acquisition parameters, the seismic acquisition survey design, is constantly subject of studies in obtaining data with the highest seismic quality, operational efficiency and cost minimization. In this paper, we propose a methodology for inverting geometry parameters of three-dimensional orthogonal land seismic surveys based on a direct search method using a mixed-radix based algorithm. In this algorithm, the search space is discretized on a mixed-radix base, which depends on the extreme values and the search resolution of each parameter. We will show how to reparametrize the orthogonal acquisition geometry elements in order to obtain the independents and integers parameters that are necessary to construct the mixed-radix base. For the optimization purpose, we define an objective function to contemplate target parameters associated with the elements of the acquisition geometry directly related to the geophysical and operational constraints. Taking in account that the mathematical functions and the objective function we define for the problem have no significant computational cost, all model space parameters are fast and efficiently tested. We applied the algorithm, using as input data, provided by a one-line roll orthogonal reference geometry, assuming a pair of geological objectives as shallow and deep targets. All selected models that meet both the proposed objectives and the constraints are organized by decreasing order of fitness so that with the mixed-radix inversion algorithm we found not only the best model, but also a set of suitable models. Likewise, with the best set of geometries, it is possible to establish a direct comparison between them, analysing their adherence to the technical and operational requirements according to the availability and degree of detail of each one. We show the top 10 best results as a table, allowing a direct comparison between all aspects of these geometries, and we summarize the results showing graphically the fitness of all selected geometries and the inverted geometry elements for the 1000 best geometries. These graphical displays provide a direct way to understand how each model behaves as the fitness decreases. The algorithm is very flexible and its application can be extended to any environment and type of acquisition geometry, and in any phase study of an area be it regional, exploratory or development. 相似文献