【作者】 郭志学；

【导师】 方铎；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2003， 博士

【摘要】 以大容重、高流速、大流量和强摧毁力为特征的泥石流骤然间将大量包含各种粒径(尤其是大尺寸颗粒)的泥沙输入主河，在短时间内改变主河水沙组成及局部边界条件，对主河水沙运动特性及演变规律等都带来重要的影响。在泥石流与主河交汇区，主河水位被壅高，泥石流中固体物质在该区段发生淤积，给交汇区及其上、下游河段一定范围内的河床地形和水流条件带来重大改变，严重时还可能形成堵江坝和堰塞湖，淹没上游农田、铁路、公路等沿江建筑物，造成大范围灾害。当洪水漫过堵江坝时，又可能发生溯原冲刷，而当堵江坝溃决时，会产生大规模的溃决洪水，造成下游长距离超常冲刷，冲毁下游农田和沿江建筑物，形成二次灾害。泥石流入汇问题与山区人民生产生活、经济建设和生命财产安全息息相关，对其进行研究具有重要的应用价值。此外，从学科范畴来说，泥石流入汇主河属于复杂的非牛顿流体与牛顿流体相互作用问题，对在交汇区复杂水沙及边界条件下主河水流和泥石流之间相互作用机制以及交汇区的水沙运动特性等的研究又具有重要的理论意义。 本文在试验的基础上对泥石流入汇主河后交汇区的水沙运动特性进行了分析和归纳，通过理论分析与试验相结合的方法对诸如水位壅高、交汇区淤积变化规律、堵江临界判别条件以及宽级配非均匀沙再起动等一系列交汇区水沙运动特性方面的问题进行了研究。论文共分六章，现分别简要介绍如下： 论文第一章对泥石流及支流入汇问题研究现状进行了回顾，指出泥石流入汇主河属于复杂的非牛顿流体与牛顿流体相互作用问题，迄今缺乏系统深入的研究，极需结合试验对泥石流入汇后交汇区的水沙运动特性开展探索性的研究。摘要 第二章主要介绍了为探讨泥石流入汇机理所进行的系列水槽试验，包括成都山地灾害与环境研究所试验，西南交通大学试验和中国水利水电科学研究院试验以及前两家所进行的泥石流堵江试验。本章对各家试验布置、设备、试验内容及观测手段做了说明，文中还对试验现象作了详细的描述，并对试验资料所显示的相关因素之间的关系做了初步的分析和归纳:通过对不同容重的泥石流入汇主河后试验现象及试验结果的差异的分析发现，泥石流容重是影响交汇区紊动强度的主要因素，泥石流容重越低，进入主河的流速越高，在交汇区引起的紊动就越强烈，反之亦然。对不同流量比的泥石流入汇试验现象的分析发现，流量比是影响主支流对比关系的主要因素，流量比越大，支流加于主流的作用越强，表现为，在泥石流容重较小时交汇区紊动加强，泥石流容重较高时结构性保持完好，容易形成堵江，主支流量相当时则对不同容重的泥石流都表现为较强烈的交汇区紊动掺混。其次，结合不同交汇角的泥石流入汇试验现象分析认为，交汇角是影响泥石流对主河作用的一个重要因素。交汇角越大，泥石流入汇后对主河的奎水作用越明显，.在交汇区越容易形成堵江现象。此外，通过对不同流速的泥石流入汇后如「区运动变化特性的分析还发现，流速是影响交汇区掺混强度和紊动强弱的主要因素之一，支流流速越高，进入主河时对主河的侧向冲击越强，交汇区紊动掺混越强烈。 论文第三章对各家试验成果进行了分析。通过对泥石流入汇后交汇区上游水位变化的分析认为，受泥石流入汇的影响，交汇区上游水位奎高，其奎高幅度随交汇角的增大而增加，在交汇角一定时则随流量比的增大而增大。此外，对交汇区淤积特性的分析指出，随流量比的增大，交汇区淤积量总体上呈增大的趋势。平均淤积深度具有随流量比的增大而先增大后减小的趋势，并表现出与主河流量有很好的相关性，主河流量越大，淤积物越分散(出现堵江情况例外)，淤积深度越小。最大淤积深度出现在主支流量相当时，最大淤积深度点多分布于支槽对岸主河下游侧，当泥石流容重较高时，则多集中分布在支槽出口附近。 论文第四章应用动量原理对交汇区水沙运动特性进行了分析，引入输运率和淤积率等概念，研究了泥石流入汇后流量比和容重比等因子变化对交汇区水沙特性影响的规律，并推导得出可以综合反映泥石流入汇后水位奎高和交汇区泥沙淤积的关系式。此外，对泥石流入汇引起堵江的各种因素所进行的分析指四川大学博士学位论文出，随泥石流入汇角、泥石流与主河的流量比、泥石流入汇总量、泥石流浆体屈服应力等的增大有利于堵江现象的发生，而主河宽度和主河比降的增大则不利于泥石流堵江，泥石流容重和泥石流与主河流速比的影响呈现一种抛物线型关系，即随参数的增大对堵江先有利而后朝不利方向发展。最后建立了泥石流堵江的临界判别式。 论文第五章探讨了交汇区淤积体在主河水流作用下的再起动问题。文中引入泥沙颗粒切点公切线与水平面的交角作为表征泥沙颗粒在床面位置的参量，根据床沙处于不同位置时受力情况，确定颗粒起动的判别条件。结合指数流速公式，推导了与泥沙粒径和位置参量(公切角)相关的非均匀沙起动流速公式。此外，从泥沙与水流相互作用机理出发，建立了可以反映泥沙颗粒对近底处水流结构影响的更多还原

【Abstract】 Debris flow, with big specific gravity, high velocity, large discharge, and strong destructive power, carry a gteat amount of sediment, especially the large-size one, into the Main River. The composition of flow and sediment and the boundary condition within the conjunction area is changed in a short time, which will seriously affect the movement characteristic of sediment and flow, and even the evolvement of the Main River. The water level of the Main River will be blocked up and the solid material of debris flow will be deposited in the conjunction area. This causes a serious change for the bed form and the flow condition in a long distance near the conjunction area. A dam and barrier lake will be built under even more serious condition. As an effect, the grain field, railway, highway and all of the construction along the river in upstream will be submerged. Even terrible, if the water overflow, it will lead to backward erosion; And if the dam outburst, major outburst flood will come forth. Because of the long distance uncommon scour, the grain field of downstream and construction along the river will be destroyed, which is a secondary disaster. It will be crowning calamity for downstream inhabitant. Thus it can be seen that to study the mechanism of debris confluence with the Main River has operation significance. Moreover, it is a complex interaction between non-Newtonian flow andNewtonian flow when debris flow joines into a Main River. To study the movement mechanism of flow and sediment under the complicated condition has theoretic significance.In this paper, based on the experiment, the movement characteristic of flow and sediment in conjunction area is studied. The height of back-water in Main River, the deposit law within the conjunction area, the critical condition of river blocking and the re-incipient of wide-size distributed non-uniform sediment have been studied in depth through theoretical analysis on the basis of experiment. The paper consists of 6 chapters. The main contents are as follows.The research status of debris flow and conflow are introduced in the firrst chapter. It shows that the interaction between debris flow and Main River is a complex problem of interaction between non-Newtonian flow and Newtonian flow, which is lack of systemic study by now. It is also be pointed out that the complex problem, especially, the flow and sediment movement characteristic in conjunction area, should be studied based on the experiment.A series of experiments aimed at exploring the mechanism of the confluence between debris flow and the Main River are introduced in the second chapter. The arrangement, equipment, and condition of the experiments are dealed with. The experiment phenomena are described in detail by charts, figures and photos. Meanwhile the relation among the relative factors is analyzed and summed up. Through the description of the conjunction experiment phenomena of debris flow with different specific gravity, it shows that specific gravity of debris flow is a main factor that influence the turbulence intensity of conjunction area. The lower debris flow specific gravity, the higher joined velocity, and correspondingly the stronger turbulent intensity. Vice versa. According to the rule of the experiment of different discharge ratio, discharge ratio is a main factor that reflects the contrastive relation of discharge of debris flow and the Main River. The bigger discharge ratio, the stronger action of debris flow to the Main River. As a result, with low debris flow specific gravity the turbulent intensity will be increased. When debris flow specific gravity is high, the structure of it is maintained, and river blocking will be producedeasily. But if the discharge is equiponderant, it will stir strongly for both high and low debris flow specific gravity. Conjunction angle is found to be another important factor which influences the mechanism of debris flow joining into the Main River. The bigger conjunction angle, the higher block-water in the Main River, and the easier rive更多还原