Trend detection in river flow series: 1. Annual maximum flow / Détection de tendance dans des séries de débit fluvial: 1. Débit maximum annuel     

《水文科学杂志》2013,58(5)

Abstract

Results of a study on change detection in hydrological time series of annual maximum river flow are presented. Out of more than a thousand long time series made available by the Global Runoff Data Centre (GRDC) in Koblenz, Germany, a worldwide data set consisting of 195 long series of daily mean flow records was selected, based on such criteria as length of series, currency, lack of gaps and missing values, adequate geographical distribution, and priority to smaller catchments. The analysis of annual maximum flows does not support the hypothesis of ubiquitous growth of high flows. Although 27 cases of strong, statistically significant increase were identified by the Mann-Kendall test, there are 31 decreases as well, and most (137) time series do not show any significant changes (at the 10% level). Caution is advised in interpreting these results as flooding is a complex phenomenon, caused by a number of factors that can be associated with local, regional, and hemispheric climatic processes. Moreover, river flow has strong natural variability and exhibits long-term persistence which can confound the results of trend and significance tests.  相似文献   

Pulse generation models for daily intermittent streamflows / Modèles de génération d’impulsions pour des débits journaliers intermittents     

《水文科学杂志》2013,58(3)

Abstract

Abstract Generating pulses and then converting them into flow are two main steps of daily streamflow generation. Three pulse generation models have been proposed on the basis of Markov chains for the purpose of generating daily intermittent streamflow time series in this study. The first one is based on two two-state Markov chains, whereas the second uses a three-state Markov chain. The third model uses harmonic analysis and fits Fourier series to the three-state Markov chain. Results for a daily intermittent streamflow data series show a good performance of the proposed models.  相似文献   

Flood forecasting and infiltration modeling/Prévision de crue et modélisation de l’infiltration     

《水文科学杂志》2013,58(2)

Abstract

Abstract The role of accuracy in the representation of infiltration on the effectiveness of real-time flood forecasting models was investigated. A simple semi-distributed model of conceptual type with adaptive estimate of hydraulic characteristics included in the infiltration component was selected. Infiltration was described by a very accurate approach recently formulated for complex rainfall patterns, or alternatively through a simpler formulation known as an extension of the classical time compression approximation. The results indicated that, for situations involving a significant rainfall variability in space, the inaccuracy in the representation of infiltration cannot be corrected by the adaptive component of the rainfall–runoff model. A preliminary analysis of the role of an approximation of saturated hydraulic conductivity to be used in each homogeneous area of the semi-distributed model used both in non-adaptive version and in real-time is also presented.  相似文献   

无结构网格上二维浅水流动的数值模拟   总被引：28，自引：13，他引：28       下载免费PDF全文

胡四一  谭维炎 《水科学进展》1995,6(1):1-9

提出在无结构网格上建立有限体积高性能格式族的统一框架,通过引入跨单元界面法向数值通量的逆风分解,将一维Osher、TVD两种通量分裂格式自然地推广至二维浅水方程组。给出了各种情况下浅水方程组有限体积法边界处理的计算公式。最后,利用该格式对穹包溢流、陆地动边界和河口潮流三个问题进行计算。结果表明,这类守恒格式具有高精度、无振荡性以及处理复杂流态过渡、自动捕俘间断和模拟陆地动边界的功能。  相似文献   

A three dimensional model of muckpile formation and grade boundary movement in open pit blasting     

R. L. Yang  A. Kavetsky 《Geotechnical and Geological Engineering》1990,8(1):13-34

Summary Formulation and case studies of a three dimensional kinematic model are presented. Thein situ overburden geometry can be simulated accurately and various initiation patterns of blasts can be modelled. The overburden geometry, hole patterns and explosive distribution are all explicit model inputs. Because the effect of explosive properties, rock mass condition and inter-row delay are very difficult to measure in terms of blast performance, these are represented in the model by control parameters which are left for calibration using field data. The output of the model is a three dimensional muckpile shape of any cross section and a contour map of grade distribution within the muckpile. Two case studies are presented which have shown that the model is a valuable tool for optimizing production blasting as well as for controlling grade dilution during blasting.  相似文献   

Tunnel blasting techniques in difficult ground conditions   总被引：1，自引：0，他引：1  

A. K. Chakraborty  J. L. Jethwa 《Geotechnical and Geological Engineering》1994,12(4):219-239

Summary The quality of tunnelling can be improved by proper blast design which takes into account the rock mass conditions. The effects of different rock mass properties on tunnel blast performance need to be assessed. The strength of the formation and joint orientation critically affected fragmentation and overbreak in a model study of blasting. Similar effects were noted in situ when the performance of a blast pattern in different rock mass conditions in the Tandsi inclines (Bihar, India) were analysed. Accordingly, the on-going blast pattern was modified for the poor ground conditions prevailing in the rest of the inclines. Improved fragmentation and smooth profile were obtained as a result; the rate of drivage improved considerably and the cost of excavation was reduced. Based on the observations in the model studies and the investigations at Tandsi, some guidelines for optimum blast design in difficult ground conditions are suggested.  相似文献   

泥湾门大桥浅海大直径嵌岩桩施工技术          下载免费PDF全文

柴云来 《探矿工程》1994,(3):28-29,31

介绍了在浅海施工直径２．２０ｍ嵌岩桩的技术问题。包括平台的搭设，用刮刀钻头与牙轮钻头钻进克取硬岩一次成孔工艺，利用冲洗液平衡原理处理浅海钻进护简断裂的成孔方法，改进浇灌清孔流程，保证浇灌质量。  相似文献   

WH-1型电镀金刚石钻头的研制及其在坚硬、致密和弱研磨性地层中的应用     

李大佛 《地球科学》1985,(3)

本文阐述了电镀金刚石孕镶钻头的研制方法和原理。此种钻头适用于坚硬、致密、弱研磨性(即所谓打滑)地层的钻进。攻克“打滑地层”的途径是:(1)降低钻头胎体耐磨性,促使金刚石出刃;(2)改变钻头底唇形状,提高金刚石破碎岩石的比压,增多孔底破碎岩石的自由面,使之易于破碎岩石。从4个钻探队、39个钻头的生产试验结果来看,上述研制工作既合理又有成效。  相似文献   

大跨预应力混凝土空间框架结构的地震振动台试验研究     

熊学玉  耿耀明  李春祥  黄鼎业 《地震工程与工程振动》2005,25(1):102-107

利用地震振动台对大跨预应力混凝土井式梁空间框架结构的抗震性能进行了实验研究。两个模型的实验结果表明：(1)大跨预应力井式梁空间框架结构可以提供大的楼层平面内刚度；(2)对称大跨预应力井式梁空间框架结构，可以不考虑耦合地震反应；(3)大跨预应力井式梁空间框架结构的竖向地震反应中心大而周边小；(4)在相同加速度但不同的地震波作用下，结构的竖向地震反应不同。  相似文献   

填充墙与钢框架协同工作性能非线性分析   总被引：5，自引：2，他引：5  

戴绍斌  余欢  黄俊 《地震工程与工程振动》2005,25(3):24-28

在试验研究的基础上，运用ANSYS有限元中的接触单元建模，对加气混凝土填充墙钢框架的结构性能进行了研究，同时与纯钢框架结构在强度、刚度、以及延性等方面进行了对比分析，结果表明：填充墙与钢框架协同工作能够改善钢框架结构的受力性能和抗震能力，这为钢结构及其围护体系的研究与推广应用提供了一定的理论依据。  相似文献