【作者】 郭国和；

【导师】 吴国雄；

【作者基本信息】 重庆交通大学 ， 道路与铁道工程， 2009， 硕士

【摘要】 西藏东南部川藏公路沿线独特而又脆弱的自然环境导致本区泥石流活动强烈,规模巨大,经常堵断其汇入的主河,形成高大的泥石流堵塞坝,蓄水溃决造成惨重的危害。本文对川藏公路南线近几十年曾经发生过的泥石流堵塞主河事件进行野外调查,运用模型试验和理论分析相结合的方法,研究泥石流堵塞坝形成后的稳定性和溃决机理,以及堵塞坝溃决后的洪水特征。论文主要结论如下:1.分析川藏公路南线4条典型泥石流沟发生的7次特大型或大型泥石流的性质和规模(其中有5次形成堵塞坝),认为影响泥石流堵塞坝溃决的主要因素为河道上游来水量、河宽、河床比降、坝体高度、坝体下游坡面倾角、坝体物质组成。2.通过研究模型试验堵塞坝溃决过程,提出泥石流堵塞坝两种溃决形式,一种是下游坡面逐渐冲刷溃决,另一种是泥石流再启动引起的坝体溃决,而后者又可以分为水力再启动和重力再启动;分析了不同溃决形式的溃口发育机理。3.根据对模型试验溃决洪水过程的分析发现,与泥石流堵塞坝溃决洪水流量关系最大的是堵塞坝的溃决形式;同时溃决洪峰流量与上游来水量成正比关系;溃决过程中的洪峰位置出现在库区水下泄30~50%的时候,平均值为38.58%;不论哪种类型的溃决,洪峰时刻出现在整个洪水历时大约1/3的时刻。4.从溃决洪水洪峰流量与库区水的势能关系出发,对Schuster的洪峰流量计算公式进行扩展,同时考虑库区形状、溃口形态以及溃决形式对洪峰流量的影响,用溃决历时T作为反映溃决形式的参数,结合模型试验数据统计,建立了堵塞坝溃决洪水计算公式:利用培龙沟泥石流堵塞坝为算例,验证了公式的正确性。5.通过模拟溃口发展与洪水流量的耦合关系,建立了泥石流堵塞坝溃决模型,模型将溃口概化为梯形,在溃口演变的模拟上进行了简化处理,不对具体的泥沙输运进行计算,而直接假定溃口尺寸扩大形式为。溃口流量采用Fread堰流公式计算。在有限差分方法的支持下模拟了培龙沟泥石流堵塞坝和扎木弄巴泥石流堵塞坝溃决洪水的发生过程,计算结果与观测数据吻合较好。在此基础上提出相应的避险减灾对策。更多还原

【Abstract】 Owing to the unique and fragile natural environment in southeastern Tibet, debris flow in this area is active, which often blocks off the mainstream in a large scale, forming the huge dam, and causing serious harm when the dammed-lake breaks. This paper investigated the recent debris-flow dam in southeast Tibet. Depending on model test and theoretical analyses, we have studied the dam stability and its outburst mechanism, and the characteristics of the flood induced by the break. Main results are as follows:1. By discussing seven events of large-scale debris flows in four gullies along south section of Sichuan-Tibet highway, from which five blocking dams resulted, focusing on the major factors impacting the dam formation, we can see that the most effective factors are discharge, river width, gradient of channelbed, height of dam, slope and the grain composition of dam.2. Two break forms of debris-flow dam are put forward through research on process of dam break in the model tests. One is gradually eroding, and the other is deposits of debris flow initiating; the latter can be classified into two forms, the first is hydraulic initiation, and the other is gravitational initiation. Meanwhile, the different mechanisms of breach-development types are studied in detail respectively.3. By analyzing the break flood process of each experiment, we can find the most important factor which affects peak break flood is the form of dam break; break flood and discharge show the direct proportion relationship; the peak flood takes place when 30~50% of the water in the reservoir is effused; and the time of peak flood takes place on 1/3 of the whole flood duration with any kind of breach.4. Considering the relationship between peak break flood and the reservoir potential energy, the shape of reservoir area, the shape of breach and the effect of break form, we set up the formula which can be used to calculate peak break flood. In this formula, break duration T is used as parameter to express the break form. 1.402 w h w0.41data of Peilong Valley debris-flow dam break validated the reliability of the formula.5. We simulated the relationship between growth of breach and flood discharge and set up numercal model for debris-flow dam break, in which we made the shape of breach as trapezia and predigeste the development of breach. We assumed that breach developed as . Take the debris-flow dams from Peilong Valley and Zhamu Valley for example, we simulated the course of flood and found that the calculated results can match with the observed data very well. On this basis, some corresponding countermeasures are proposed for risk mitigation.The paper is supported by the National Science Foundation (Grant No.40771024) and Western Transportation Construction Project Foundation (Grant No. 200631879284).更多还原