【作者】 张治昊；

【导师】 胡春宏；

【作者基本信息】 中国水利水电科学研究院 ， 水力学及河流动力学， 2005， 硕士

【摘要】 1986年以来,黄河口水沙过程发生了变异,新的水沙条件下黄河口演变规律和发展方向成为一个亟待研究的新课题。本文在研究黄河口水沙过程变异的基础上,深入分析了水沙过程变异引起的黄河口演变的剧烈响应及其演变机理,取得了如下成果: 1.运用数据平滑处理方法分析得到黄河口1950-2000年的水沙过程以1968年和1986年为变异分界点分三个阶段。对比分析三阶段水沙特征可知,黄河口水沙变异过程复杂,其年际间、年内分配、水沙搭配、来沙组成、典型水文特征均发生了变化,黄河口水沙变异是上述各种变化的综合体现。构建了黄河口水沙变异综合参数ζ,可全面表征黄河口综合水沙条件。建立了三个阶段综合参数毛与来水来沙的关系式,证实了黄河口水沙过程发生了变异。 2.黄河口水沙变异,尾闾河道严重萎缩,其冲淤过程、纵比降调整、横断面形态等均发生了变化。概化的尾闾河道萎缩纵向模式曲线方程为f=-0.00007x~3+0.01x~2-0.14x+7.6,横向模式如图3-10所示。造床流量的减小、河床阻力的增大、河道冲淤特性的改变、河海耦合动力减小促进了尾闾河道萎缩的形成;萎缩形成的纵剖面、横断面进一步降低了输水输沙能力,加剧河道萎缩的发展。引入了尾闾河道萎缩的判别指标Tn,以Tn=0.2,0.3,0.45作为河道萎缩发展阶段划分点,为治理尾闾河道萎缩提供了控制标准,当Tn达到0.2时,标志着河道开始萎缩,应加强观察;当Tn升高到0.3时,应采取一定的工程措施减小河道萎缩程度;当Tn升高到0.45时,必须采取有力的工程措施大幅度减小河道萎缩程度。 3.黄河口拦门沙的发育演变与水沙条件密切相关。水沙较大时,拦门沙纵向淤进快、横向摆动频繁、发育尺寸大;水沙变异,拦门沙纵向淤进慢、横向摆动弱、发育尺寸小;水沙减少到一定程度,拦门沙表现为蚀退。回归分析得出的拦门沙淤进与尾闽河道萎缩的关系表明尾闾河道萎缩不利于拦门沙的发育。综合分析得出拦门沙的立体动态推进模式为:一段时间内纵向延伸为主,横向摆动为副,下一段时间内横向摆动为主,纵向延伸为副,如此周而复始,不断向海域中推进。 4.依据黄河口演变对下游河道的反馈影响的典型发展过程,概括出反馈影响发展分溯源冲刷和溯源淤积两个阶段,溯源冲刷表现剧烈,溯源淤积表现较弱。反馈影响发展长度与改道初期河道缩短长度、河道淤积延伸长度、时段水沙条件、河道边界条件、大型水利枢纽调节等因素有关,利用多元回归分析建立了反馈影响长度综合关系式。反馈影响的发展传递是通过相邻局部河段自下而上的连锁调整完成的,传递过程中纵比降调整的物理图形是折线,越向上游比降变化越小。更多还原

【Abstract】 The variation of flow and sediment has been appeared in the Yellow River estuary sincel986. Under the new condition of flow and sediment, the law and direction of evolution are becoming a new problem needed to solve urgently in the Yellow River estuary. By studying the variation of the processes of the flow and sediment, the response of the evolution is in-depth analyzed in the Yellow River estuary. The main works of thesis are illustrated as follows:1. The processes of flow and sediment from 1950 to 2000 are divided into three phases with the boundary of 1968 and 1986 in the Yellow River estuary. By analyzing the characteristics of flow and sediment of three phases, it can be concluded that the variation of the processes of flow and sediment were complex in the Yellow River estuary, the characteristics of year-by-year, distributing in one year, arranging in pairs or groups, composing of incoming sediment and the typical characteristics of hydrology changed all, the variation of flow and sediment in the Yellow River estuary was synthetic embodiment of all changes mentioned above. A synthetic parameter named ξ is formed, ξ can express the flow and sediment condition of the Yellow River estuary. The formulas of the relationships between ξ and the incoming flow and sediment of three phases were different., it proved that the variation of the processes of flow and sediment happened in the Yellow River estuary.2. With the variation of flow and sediment, tail channels atrophied badly in the Yellow River estuary. The processes of erosion and deposition, adjusting of vertical section, modality of cross section changed all in the tail channels. Longitudinal mode curve of the atrophy of tail channels generalized is f =-0.00007x3+ 0.01x2-0.14x+7.6, transverse mode is generalized as the fig 3-10. The atrophied reason comprises reducing of dominant discharges increasing of resistance of riverbed changing of characteristic of erosion and deposition, reducing of coupling power of river and sea; after atrophy of tail channels came into being, vertical section and cross section atrophied would reduce the transporting power of flow and sediment, it would prick up atrophy of tail channels. A distinguishing target named Tn is imported, Tn=0.2, 0.3, 0.45 can be regarded as limits of seedtime of the atrophy of tail channels, it will be as reference value of controlling atrophy of tail channels.3. The relationship between the estuarine sandbar evolution and flow and sediment conditions is correlation nearly. When the incoming flow and sediment are big, the speed of longitudinal advancing of the estuarine sandbar is fast, the transverse swing of the estuarine sandbar is frequent the size of the estuarine sandbar is big, with the variation of flow and sediment, the speed of longitudinal advancing become slow, the transverse swing become puny, the size become small, when the flow and sediment reduce definite degree, the body of the estuarine sandbar become eroding. The relationship between the advancing of the estuarine sandbar and the atrophy of tail channels reflects that the atrophy of tail channels goes against the growth of estuarine sandbar. By synthetic analyzing, the solid dynamic advancing mode of the estuarinesandbar is gained in the Yellow River estuary . During period of time; the longitudinal advancing is primary; the transverse swing is secondary; during next period of time; the transverse swing is primary; the longitudinal advancing is secondary; the estuarine sandbar advance perpetual in the direction of ocean as this.4. The evolution of the Yellow River estuary bring the feedback influences to the lower reaches of the Yellow River; according as the typical developmental process of the feedback influences; the developmental process of the feedback influences comprises two phases: the first is eroding trace to the source; the second is depositing trace to the source; the characteristics of the two phases are different; eroding trace to the source is intensity; depositing trace to the source is faintness. The development of the feedback influences is related to the extending and shortening length of the reaches the flow and sediment conditions the border conditions of the channels regulated by the large hydraulic hinge etc. By choosing the farthest length of eroding trace to the source as the length of the feedback influences; a formula of the feedback influences is gained. The transferring of the feedback influences is accomplished by the concatenate regulating of reaches; the physical figure of regulating of longitudinal grade is a broken line.更多还原