【作者】 陈春光；

【导师】 姚令侃；

【作者基本信息】 西南交通大学 ， 道路及铁道工程， 2004， 博士

【摘要】 饱含大量泥沙石块的泥石流进入主河，往往会堵断河流，淹没上游农田、铁路、公路等沿河建筑物，造成大范围危害。另一方面，泥沙石块在河道中的堆积，控制着入汇口附近的水沙交互作用和河床形态变化，变迁型河段对公路、铁路的危害是全局范围的。 从力学性质上划分，一般泥石流属于非牛顿流体，而河水则通常被看作是牛顿流体，泥石流入汇主河，其汇流后的运动特征与牛顿流体之间的交汇问题不同，是一种非牛顿流体与牛顿流体之间的汇流问题，泥沙的堆积与输移、主河水流的变化以及河床的改变等均表现极为复杂。本文首先通过野外实地考察和室内模型实验，来探明两种不同流体交汇时相互作用特点，然后建立在不同交汇条件下泥石流和主河水流交汇的流动模型，并研究可行的求解方法。 在野外考察方面，主要围绕云南小江流域，调查了泥石流与主河交汇现状及其泥石流活动对铁路和公路的影响，分析总结了实际观测到的交汇特点。 为了探明泥石流与主河交汇的相互作用机理，本文重点介绍了所开展的室内模型实验。首先研究了两场交汇试验的相似性问题，对于泥石流入汇主河水流，其相似性主要应考虑主支流的几何因素(包括交汇口夹角)、入汇前泥石流物理特性、主支沟各流体运动学和动力学因素。实验的重点放在交汇初期汇流部的流动特点，对于一般稀性及粘性泥石流，交汇角、支沟与主沟相互关系、主支流流量比的影响非常大。根据泥石流在交汇区的流动特性，试验得出两种不同的交汇模式，即“有分层交汇”模式和无明显分层的“潜入式交汇”模式。试验还表明有分层交汇时泥石流的运动与泥石流在无水流作用下的运动有着本质的不同，而潜入式交汇模式与异重流有相似之处。模型试验得到了潜入式交汇泥石流龙头运动速度变化规律和龙头几何特征，初步探明了分层交汇的动力学机理和上下层速度差的影响因素。 在试验研究的基础上，针对潜入式交汇模式，运用质量守恒方程和动力学方程建立了入汇泥石流龙头的运动方程。计算结果得到以下结论：(1)当主河水流弗劳德数比较小(Fr＜0.35)时，入汇主河泥石流龙头运动速度近似以线性下降，且与试验值吻合较好；(2)混合流粘滞系数η和绕 西南交通大学博士研究生学位论文第日页流系数CD对龙头运动速度影响较大;(3)泥砂沉降速度w，对龙头内部体积比浓度有显著影响。 对于复杂的有分层交汇情况，本文从经典流体力学和非牛顿流体力学理论出发，建立统一的能反映交汇区流动的控制方程，在此基础上，采用标志网格法(MAC法)和质点网格法(PIC法)，结合现有的有关泥石流、泥沙等浆体的流变关系和流变参数，提出了一种计算交汇区流场和泥沙沉积与输移的祸合分析方法。通过计算实践表明:文中所提出的祸合计算方法是可行的，所建立的二维和三维模型，可以从不同的角度刻画了交汇区水面的变化、泥沙沉积与输移特性。 考虑到泥石流在结构上具有多样性，本文在对传统离散单元法(DEM)进行分析的基础上，提出了适用于计算泥石流运动的三维离散单元模型，运用此模型计算了主河在无水(或弱水流)条件下，泥石流堆积过程与堆积扇形态。在此基础上，提出了泥石流(采用离散单元法)与主河水流(流体力学方法)交替计算的祸合模型，模型中重点考虑了堆积体与水流交接面单元格中泥沙沉积与输移，并按单元格中的流动状态和泥沙浓度来确定泥沙的沉积与输移。运用改进后的模型计算了无水和有水流作用下的两种堆积过程，其堆积体的纵向坡面变化、堆积扇的几何形态、泥沙浓度分布等，均得到了较详细的刻画。更多还原

【Abstract】 When debris flow, which contains large quantities of stone, sand and clay particles, enters into a Main River, the river is frequently blocked, and farmland, railways and roads, and all of the construction along the river upstream will be ruined. Also, stone and sediment deposited in the Main River, it has an important influence on the movement of sediment and flow, and river channel may change. As a consequence, the changing river will affect construction of overall the railway and highway situation.From mechanics point of view, debris flow is usually classified as Non-Newtonian flow, and water in river as Newtonian flow. Thus, there is a complex interaction between Non-Newtonian flow and Newtonian flow, when a debris flow joins into a Main river. The transportation and deposit of sediment and water flow within the junction area is much more complex then between water flows. In this paper, first we investigate the mechanism of confluence between debris flow and the main river, Based on field observation and experiment, then deduce an equation for flow and sediment in the junction area with different conditions of confluence, and study a solution of the equation.First, we investigated Xiaojiang River, a well known area of rainfall debris flow occurrence, located in Yunnan Province in China. From field investigation, we gathered useful data about confluence between debris flow and the main river, and the effect of debris flow action railway and highway.To study the mechanism of confluence between debris flow and the main river, we carried out experiments. First, model similarity laws for model tests are studied. Flow phenomena at the junction area and experimental data are also reported. Based on the experiment, two patterns in confluence between debris flow and Main River, stratification flow and submerging flow, are put forward. The velocity changes and shape of debris flow head submerging into water, and mechanism of stratification flow in the confluence are examined.Based on the field observation and the experiment, the theoreticalequation to describe the movement of debris flow head in the submerging flow pattern is established, and the calculation parameters are studied in turn.The following conclusions can be drawn from the simulation:1. In the case of a low Froude number (Fr<0.35), the velocity of debris flow head submerging into water exhibits an approximately linear decrease, which is in good agreement with the experimental data.2. The viscosity ( ) and drag coefficient (CD) have a large influence upon the speed of debris flow head.3. Sediment settling velocity (wS) has pronounced effect on the concentration (Cv) in the body of debris flow head.With regard to stratification flow, based on theories of both classic fluid mechanics and non-Newtonian fluid mechanics, this thesis has first established a two-dimensional and three-dimensional governing equation with the tensor form, to describe the confluence of debris flow and main channel.Using the present rheologic equation and parameters of both debris flow and flow with hyperconcentration of sediment, and the MAC and PIC methods, a coupling numerical simulation which can solve this equation has been proposed.Calculated results show that this method is really feasible for analysis of the movement characteristic of flow and sediment in a conjunction area. The 2-D and 3-D calculating model can depict details of different aspects, from different angles.Considering that the characteristics of debris flow body are many and varied, this paper discusses the conventional Discrete Element Method (DEM). A three-dimensional model for simulating debris flow is put forward first. Using this model, the debris flow deposit process and the accumulative fan form are simulated under both conditions, the small water flow in the main channel and no water action.Then, a coupling model is established, in which the calculation alternates between debris flow with DEM and the main channel with the hydromechanics method. The sediment deposit an更多还原