冲积河道纵向冲淤和横向变形数值模拟研究及应用

【作者】 王新宏；

【导师】 沈晋； 曹如轩； 钱善琪；

【作者基本信息】 西安理工大学 ， 水文学及水资源， 2000， 博士

【摘要】 冲积河流中，河槽的纵向形态和横向形态都处于不断的冲淤调整之中。河流变形的数值模拟需要兼顾河槽的纵向冲淤和横向变形两个方面。许多河道变形的数学模型仅能够模拟河道的纵向冲淤变形，无法模拟因河岸（或滩地）坍塌造成的河槽横向变形过程。 本文首先回顾了前人在河流横向变形物理机理及数值模拟方法方面的大量研究成果。然后以冲积河流为对象，通过对河槽冲淤调整过程中河岸（或滩地）坍塌下滑的土动力学机理、岸壁泥沙坍塌的数量及其物理特性和冲淤特性等的分析研究，提出了一套可以同时反映河槽纵向冲淤和横向调整变形的河道变形模拟方法。以此为基础建立了一个可以模拟多沙河流上水库及河道冲淤演变过程的准二维泥沙数学模型。该模型首先通过联立求解一维水流方程和简化平面二维水流方程，得到水力要素在横向及纵向的分布，水流计算的结果用于河槽纵向和横向的泥沙冲淤计算。河槽的纵向冲淤变形是通过联立求解分粒径组泥沙的连续方程和河床变形方程得出的，河槽的横向变形是通过联解河岸（或滩地）的稳定性和水沙输移计算结果得到的。求解出某时段的河岸泥沙侵蚀量后，将其分成床沙和悬移质两部分。床沙部分作为本时段的淤积量就地淤积，悬移质部分作为侧向悬移质输沙率参与下一时段河槽的纵向泥沙输移计算，以此反映河槽纵向冲淤与横向变形的相互作用。本文还对冲积河流河槽纵向冲淤及横向变形数值模拟中的有关问题进行了探讨，主要之处为：（1）探讨了分组泥沙的恢复饱和系数与混合沙综合平均恢复饱和系数之间的关系，得出了分组沙的恢复饱和系数与其沉速成反比的初步结论；（2）详细论述了河岸水力侵蚀和重力侵蚀的物理过程和机理，并提出了相应的模拟方法；（3）探讨了河岸泥沙失稳崩塌的纵向范围、水位变化对河岸稳定性的影响以及塌岸泥沙的冲淤特性等问题。这些探讨是很有价值的。 利用三门峡水库1960～1990年的实测资料，对本文建立的准二维泥沙数学模型进行了测试和验证，计算结果与实测值相符合。利用所建模型对小浪底水库不同运用方案的水库泥沙冲淤过程进行了预测计算，并研究了三门峡水库运用方式对潼关高程的影响。更多还原

【Abstract】 This thesis reviewed at fist the existing results of the physical mechanisms and simulationtechniques of lateral river channel changes. In order that the numerical model developed be basedon sound foundations, Several fundamental aspects relating to cohesive river bank erosion andcollapse in alluvial rivers, such as the lateral f1uvial erosion at the base of the banks, the stabilityanalysis of riverbanks, the physical properties of failed bank materials, and the interactions betweenlateral and longitudinal channel deformation, were investigated .The quasi-2D model developed inthis thesis can simulate both the lateral and longitudinal channel deformations, and is applicable toheavy sediment carrying alluvial rivers with sand bed and cohesive riverbank materials. The lateraland longitudinal distribution of hydraulic variables are obtained, at the first step, by coupling the1D gradually varied flow equations and the simplified 2D flow equations. Secondly, thelongitudinal channel deformation is obtained by solving the sediment continuity and river beddeformation equations for every grain size group. The lateral channe1 deformation is determinedfinally by the analysis of river bank stability of both sides. The materials of the bank erosion in atime step is divided into two groups, bed material and suspended load. The former deposits on theriverbed in that time step, and the later is transferred to the sediment transport equations in the nexttime step, there-by the interaction between the lateral and the longitudinal channel deformation isaccounted for. Besides, several important issues relevant to the modeling of the lateral andlongitudinal channel deformation in alluvial rivers are discussed. The salient point are as-follows:(1)The coefficient of saturation recovery(CSR) for non-equilibrium transportation of non-uniformsuspended load is investigated, and the primary conclusion is that the CSR of a size group is ininverse proportion to its particle size; (2) It is discussed in detail the physical processes andmechanisms of both the fluvial and the gravitational bank erosion as well as the numerical methodof them; (3)The discussions of the water surface elevation impacts on the bank stability, thelongitudinal extent of the bank failure, and the physical properties of the failed bank materials arealso worthy of note.The proposed numerical model has been used in the simulation of the river channeldeformations during l960 to l990 in the San-men-xia reservoir. The computed results of the modelare consistent well with the measured ones. Finally, the model is used for predicting the riverchannel changes in Xiao-lang-di reservoir at four different application manners.更多还原