【作者】 秦毅；

【导师】 李怀恩； 沈冰；

【作者基本信息】 西安理工大学 ， 水文学及水资源， 2009， 博士

【摘要】 近20多年来,受气候和人类活动影响,宁蒙河段的河流环境发生很大改变,从而也引发了人们对水利工程开发建设的争论,其中争论焦点之一就是采用何种利用方式,使其既能有效利用水资源,又能改善宁蒙河段下游河道的淤积现状乃至完善整个黄河的防洪体系。由于缺乏对水沙输移特点及河床演变规律的系统认识,因此目前已有研究还不足以回答上述问题。另外,宁蒙河段河流属于中少沙,粗沙河流,应具有不同于黄河下游和低含沙河流的泥沙输移特性。因此探讨宁蒙河段的水沙互动响应,不仅对宁蒙河段淤积治理措施及防灾减灾研究有意义,对丰富泥沙运动力学和河床演变学也是一种贡献；对冲积河流的水位预报方法研究起理论支撑作用。在基本规律的研究基础上,论证、探讨合理的治理策略,更具有现实意义。为此,本论文一改以往主要基于长时段,如年、汛期、非汛期的水、沙平衡,以输沙率、河道冲淤为起点的研究方式,变为依据河流动力学理论,从研究泥沙组成及运动性质出发,探讨河床塑造核心期,即洪水期包括凌汛期洪水过程的水、沙、河床形态的互动响应关系与机理,研究河道环境与河道萎缩间的因果层次关系,进而分析论证治理策略。针对利用输沙平衡理论量化冲淤存在的不足,寻求能够随时跟踪表达横断面形态冲淤变化的量化方法。本论文研究获得如下成果。(1)从泥沙组成特性和运动特性出发,依据河流动力学理论和统计学的假设检验,界定了河道的泥沙组成、运动特性与运动形式。(2)提出了洪水过程中河道冲淤变形的物理图形。由实测资料分析结果证明这个图形真实存在。这更有助于直观、清楚地认识多沙、粗沙河流变化特性。(3)剖析了夏季不同类型洪水在河流纵向和横向上的冲淤特点及成因,以及凌汛期洪水的输沙特性及成因。(4)分析得出宁蒙河道河流环境变化与河道响应状况,并依此,结合洪水期水沙运动特性,指出河道萎缩成因的层次。(5)将理论分析与实测资料分析结合,从基本理论、与黄河下游泥沙条件对比的差异、中常洪水对河道断面形态的影响、人造洪水过程形状对河道冲淤的影响和河道冲刷用水量这5个方面的分析表明,人造洪水冲刷河槽的方式值得商榷。(6)根据宁蒙河道泥沙运动和凌汛期洪水输沙特性,提出粗细分治,即粗颗粒泥沙与细颗粒泥沙分开治理的思想；推荐利用低温期水流与新型自排沙廊道结合排沙的河、渠、水库防淤治淤措施,并从机理上阐明这一排沙组合的合理性。同时以推荐的小浪底水库减淤应用为例,指出了它的应用前景。本论文研究的主要创新之处表现在如下几点。(1)黄河“驼峰”现象是一种尚不被认识的现象。本论文依据动量守恒原理和河流演变趋于均衡性原理及单位时间河流功率最小假说,分析提出黄河“驼峰”现象的产生机理之一,即人造洪水过程形状引起的泥沙堆积(2)提出横断面冲淤面积量化计算方法。该方法完全量化了前后时刻横断面面积因冲淤(包括悬移质和推移质)引起的变化,可以随时跟踪整个洪水过程中的断面变化情况。一改过去“只有在大断面测量之后”才知道冲淤情况的局面。与常用的输沙率平衡法相比,不受漏测近河底输沙量的影响,也不受上下游输沙过程难以完全对应所带来的不确定性影响。(3)将河床冲刷率公式推广应用于河流冲刷需水量计算。与基于输沙平衡方程的用水量计算方法相比,它可以有效考虑水流,河槽边界及泥沙粒径的影响。基于输沙平衡方程的用水量计算方法,既无法将三者区分开来,又受到“漏测”的困扰。更多还原

【Abstract】 The place around Ningxia-inner Mongolia river bend of the Yellow River (Ning-Mong section in short) is a relative developed place within west China, where live ethnic minorities as the Hui, Manchu and Mongolian. Since the last 20 years, climate change and human activities there have affected the river environment in the results of the river serious shrinkage and frequent ice flood disasters, which bring great loss of people properties and big influence in society. Therefore, debates are caused from the local requirement for the development of water resources. One of the focuses is on which measure can be adopted in good use water resources and at same time in improving the river shrinking situation and even the whole flood control system of the Yellow River. However, since the research work has been down before long, the existing research results are unable to answer the above question due to lack of adequate knowledge on the laws of the riverbed scour and deposition. Apart from that, river of the Ning-Mong section is a medium scale sediment river and a coarse river as well. It should have different sediment transport characteristics from that of the downstream channelof the Yellow River or a river of small sediment concentration. Studying the interaction of river flow with sediment and river deformation process is meaningful not only to enrich river mechanics and riverbed evolution, but also to support theoretically a method research for water table forecasting of an alluvial river. Especially, it would be more important practical meaning if a soundly measure of the shrinkage control is proposed from the study.For the reasons above and considering strong riverbed deformation occurring in flood season, this thesis focused on studying the interaction process among flow, sediment and bed form happening in flood including ice flood period. The research work started at demarcating the river sediment fraction and sediment mobility instead of a tradition that starts at analyzing sediment delivery rate and sediment transportation equilibrium based riverbed scour-and-fill amount, and then found and brought the river environment causes of the shrinkage into order. Finally, the availability of proposed shrinkage control measures for the Ning-Mong section was discussed in detail. Meanwhile, in connection with the shortage existing in the sediment transportation equilibrium based quantification of an amount of scouring and deposition, a new method should be found by this thesis in order to show the river cross section deformation in quantification following flood process.The practical research results gained from this thesis are listed as follow.(1) Based on sediment mechanics and hypothesis test, the sediment fraction, mobility and motion style had been qualified.(2) Put forward the physical process mode of riverbed scour-and-fill during flood, which had been shown existed in nature by observations. This is helpful to know the nature of heavily burdened coarse river change.(3) Indicated the characteristics of sediment transport in ice flood and its formation mechanics.(4) Found out the environmental causes of the shrinkage and put them into order.(5) Proven the measure of manmade flood for the Ning-Mong section deposition control to be unavailable on five aspects which are the basic theory, the difference of sediment conditions from that in the downstream of the Yellow River, effect of medium and normal flood on bed form, the ship of manmade flood effect and sediment-scouring water volume.(6) From the laws of sediment motion and the characteristics of ice flood sediment transport, an idea about the river deposition control was brought out which is to deal with coarse and fine particles differently. Therefore a measure which is a new desilting gallery used with low temperature water flow was proposed to evacuate coarse in a river or in a cannel, or in a reservoir. Its prospect had also been showed with proposed application in the Xiaolangdi reservoir desilting as example.This thesis’s key innovative points include:1) Throw a light on the "hump" phenomenon in the downstream of the Yellow River with the theory of momentum and taxis of an alluvial river motion to equilibrium.2) Propose a new method to calculate the change quantity of cross section area leading from scouring or deposition at any time in flood period, which can be traditionally gained by measuring the section after flood. Compare with the traditional method of sediment load balance, the new method would not be influenced by missing sediment load near bed and by uncertainty from lacking agreement between upstream and downstream hydrographs.3) Exploit the Wang’s scouring rate formula to calculate sediment-scouring water volume. In this way, factors as flow, particle size and boundary ship can be considered.更多还原