【作者】 李凌云；

【导师】 吴保生；

【作者基本信息】 清华大学 ， 水利工程， 2010， 博士

【摘要】 以黄河流域冲积河段为研究对象,以基础理论研究和数据资料分析相结合为手段,探索河道主槽平滩流量随水沙条件变化的响应调整规律,研究了维持河道主槽一定平滩流量大小的水沙条件,论文对于揭示冲积河流的河床演变规律具有重要意义,为科学的河流治理提供了参考依据。选择黄河流域三个冲积河段:黄河内蒙古河段、黄河下游河段和渭河下游河段为研究对象,分析表明,各冲积河段均存在来水来沙量减少和水沙年内分配均匀化的明显趋势,均出现了不同程度的主槽萎缩、平滩流量减小、河道排洪输沙能力下降的现象。基于一维河床冲淤变形方程和不平衡输沙方程,推导了冲积河流滞后响应模型的基础方程,为滞后响应模型提供了理论支持。对平滩流量滞后响应模型的结构和参数计算方法进行改进:(1)调整模型中前期水沙条件的影响权重;(2)推导出反映不同年份之间河道调整速度差异的模型方程;(3)推导出同时考虑汛期和非汛期水沙条件影响的模型方程;(4)改进模型参数的计算方法,使其能一定程度上反映来水过程的影响。应用改进后的模型得到了适用于各河段的平滩流量计算方法,计算结果与实测值符合很好,模型具有较高的计算精度。平滩流量的响应调整受到包括当年在内前期一定时期内水沙条件的共同影响,且不同河段受前期水沙条件影响的时间范围不同。分析了平滩流量的响应调整模式,对“累积作用”和“滞后响应”两个概念的本质联系和区别进行探讨,认为前期水沙条件影响的时间范围和平滩流量的响应调整时间在数值上相等。研究了平滩流量响应调整时间的变化规律,就黄河流域而言,河段间汛期平均悬移质含沙量的差异是导致平滩流量响应调整时间长短各异的关键因素。从能量平衡出发分析了挟沙水流的能量耗散机理及水流塑槽和输沙能量的分配原理,建立了同时考虑河道塑槽需求和输沙需求的塑槽输沙需水量计算方法。以三黑小的来水来沙为输入条件,得到了黄河下游河道塑槽输沙需水量的计算公式,并给出了维持黄河下游平滩流量为4000m3/s的塑槽输沙需水量区间。更多还原

【Abstract】 Combining the basic theory and measured data analysis, studies are carried out on the adjustment of bankfull discharge (BD) responsing to the variation of incoming flow and sediment conditions (FSC) of Yellow River (YR). FSC to maintain an aimed value of BD are proposed. This study reveals the trends of fluvial river processes and provides a reference for river training in a better way.Three alluvial reaches of Yellow River basin, e.g. the Inner Mongolia reach, the lower YR, and the lower Wei River the biggest tributary of YR, are selected as samples to analyze the variations of flow, sediment and the characteristics of river channel morphologies in recent 5 decades. It presents visibly decrease of runoff and sediment load in the YR basin that led to a continuous shrinking of main channel, declining of BD, and degrading of capacity for flood conveyance and sediment transport.According to the 1-D equation of bed deformation and non-equilibrium sediment transport, a basic equation for the delayed response model for alluvial river is deduced. Besides, the model is further improved in the framework and its parameter determinations: as 1) Reapportioning the effect weights of FSC of previous years with a more reasonable distribution; 2) Introducing a variableβinstead of constant to reflect the different rate of channel adjustment for different years; 3) Considering the FSC of both flood and dry season; 4) Taking account the effect of flow process in to the BD. Methods of BD calculation for selected river reaches are provided based on the modified model. Tests against measured data indicate that the modified model can accurately describe the adjustment of BD.Result of analysis reveals that the adjustment of BD is affected by the FSC of present year and that of earlier years as well. However, the length of years should vary from case to case. It is equal to the time period of BD adjustment, on the base of the adjustment process of BD and relationship between“accumulated effects”and“delay response”. Studies show that the annual sediment concentration of flood season plays an important role in determining the time period in the YR basin.The energy dissipation mechanism of sediment-laden flow and the energy allocation for both channel forming and sediment transport (CFST) is studied, and method for the calculation of water demands for CFST is developed based on the energy balance principle. Furthermore, a method for the calculation of water demand for CFST for the whole lower YR course is proposed by utilizing the FSC at San-Hei-Xiao as the input variables. As an example, the range of water demands for the forming and maintenance of BD of 4000m3/s is provided.更多还原