【作者】 刘翠容；

【导师】 姚令侃；

【作者基本信息】 西南交通大学 ， 道路与铁道工程， 2014， 博士

【摘要】 随着全球气候变化异常和人类社会经济活动的不断增强,极端天气和地质事件增多,尤其是汶川地震后的4年里泥石流活动非常活跃,暴发了数次特大规模泥石流,汛期的实践表明,泥石流是震后最为活跃的灾种,泥石流堵河成为一种频繁的灾害事件。本文面对极端激发条件和汶川地震震后成灾环境急剧演变状态下,我国特大泥石流灾害频发的严峻形势,面向国家山区建设中急需解决的泥石流防灾减灾问题,以岷江映秀至汶川段多处泥石流沟堵江,以及舟曲、清平特大泥石流灾害为背景,采用现场调查、理论分析、模型试验和数值模拟相结合的技术手段,研究泥石流堵塞大河的特点及机理,建立泥石流堵塞大河各种模式的判据等,为城镇和重大基础设施防御泥石流堵河引发的大范围灾害提供科学依据。主要进行了以下工作并取得了研究成果：(1)基于现场调查和查阅文献收集的资料,归纳出泥石流堵塞大河存在着潜坝壅堵、堰塞坝局部堵塞和堰塞坝全堵三种堵河模式,并提炼出了三种堵河模式的特点及成灾模式。潜坝壅堵主要发生于运动速度较高的稀性泥石流或者容重较小的粘性泥石流,其特点是泥石流始终在水下运动,泥石流停积体淤高河床,改变河道纵断面,以上游壅水形式造成淹没灾害。以堰塞坝形式造成大河堵塞主要发生于粘性(或高浓度)泥石流。一般情况的局部堵塞,主要是堰塞坝束窄水流、改变河道,影响大河行洪能力；但当堵塞系数大于0.8以后,由于泥石流严重推移大河水流,可能造成异岸冲刷灾害。泥石流完全堵断大河的事件不多,但一旦发生,堰塞湖会造成上游淹没灾害,溃坝时会造成下游超常洪水；在宽谷段甚至会迫使主河改道,形成更大范围的严重灾害。(2)针对岷江流域泥石流多半是以堰塞坝形式局部堵塞主河的现象,运用大型室内水槽试验再现了交汇角为900时粘性泥石流入汇主河的过程,揭示了泥石流入汇主河过程的特点及泥石流堵塞大河的机理。重点研究了堰塞坝局部堵塞大河的特点,试验结果表明：泥石流入汇主河的运动过程是后续泥石流逐步推移龙头运动的过程；泥石流总量对堵河有重要的影响,总量越大堵河越严重；在泥石流堵河过程中,主河流速、堰塞坝物质流失量和上游水位壅高值都随堵塞系数呈非线性规律：主河流速随R先增大后减小,当R小于0.8时,堰塞坝的物质流失量少,上游水位壅高值呈线性增加,当R大于0.8时,堰塞坝的物质流失严重,上游水位壅高值呈指数增加。(3)根据泥石流堰塞坝堵河模式的特点,基于水沙动力过程,以泥石流在坡度变化沟道内的运动方程为基础,考虑堰塞坝和主河水流的相互作用,给出了泥石流在主河中运移距离的计算公式；鉴于泥石流堵塞大河过程中物质流失严重的现象,根据水槽实验数据确定了流失系数；以周必凡提出的泥石流堵断主河总量的计算公式为基础,提出了按流失系数加以修正的泥石流阻塞大河物质总量条件。从而建立了基于动力学方程、物质总量的泥石流堵塞大河综合判据。(4)基于堵塞系数R对于预估泥石流堵河灾害效应的关键作用,以模型试验数据为依据,导出了堵塞系数R的表达式,此式可用来预估泥石流堵河的程度,也可作为泥石流局部堵塞大河的另一判据,可用来指导泥石流防治工程的设计。(5)根据潜坝壅堵模式的特点,基于异重流理论导出了泥石流龙头运动简化方程,基于有坎宽顶堰模型给出了潜坝壅堵上游水位计算式；对影响泥石流龙头运动的各个因素进行了单因素分析,分析表明泥石流粘滞系数和切应力对龙头运动速度影响不明显,绕流阻力系数对龙头运动速度影响最大；给出了泥石流龙头在主河里的运移距离随时间的变化曲线,在此基础上给出了潜坝堵河的最小固体物质总量计算式。(6)根据泥石流堰塞坝堵河模式的成灾模式,运用数值模拟方法分析主河在不同堵塞系数时的水流流场,再基于信息熵原理定量地分析主河流场有序度,得出当堵塞系数R为0.80-0.9时,主河流场熵值急剧下降,表明流场有序度不断增高,流向以偏向异岸为主,且此时水流速度大,水流偏转又集中发生在近河岸处,对河岸具有很强的冲刷能力,R=0.80可作为主河水流偏转冲刷异岸的临界点,把堵塞系数R>0.80作为泥石流局部堵河异岸受灾判据。通过岷江流域银杏至映秀段泥石流堵河实例验证,表明数值模拟结果与实际情况吻合,泥石流局部堵河异岸受灾判据可行,进而提出了泥石流灾害效应与判据框图。基于堰塞坝局部堵塞主河使上游水位壅高致灾的现象,给出了水位壅高值计算式,为计算淹没范围提供了依据。(7)针对不同堵河模式的灾害效应,提出相应的减灾对策。对于全堵模式首先考虑抬高淹没区线路标高,若受其他条件限制无法实施时,则考虑限制泥石流入汇主河的流量和总量,以减轻或消除泥石流堵塞大河。对于局部堵塞模式主要考虑异岸受灾,采用导流工程、支挡工程等工程措施保护异岸线路工程免受冲刷。对于壅堵模式,则考虑小范围抬高线路标高。更多还原

【Abstract】 With global climate change anomalies and growing human social and economic activities,extreme weather and geological events increase cont-inually.In particular,debris flow is very active in the four years after the Wenchuan earthquake,and very large scale debris flow breaks out several times.The practice in flood season shows that debris flow is one of the most active disaster species, and debris flow blocking the river has become a frequent disaster.This paper faces the grim situation of large debris flow taking place constantly in China in the extreme excitation conditions and the state of disaster forming environment changing rapidly,faces the problem of debris flow disaster prevention and mitigation in the mountainous area con-struction.Based on the background of debris flow blocking river at many points in the Min Jiang River from Yingxiu to Wenchuan and Zhouqu、Qing-ping large debris flows, the thesis analyzes the mechanism of debris blocking the river and disaster chain effect, by the methods of field survey, theoretical analysis, model test and numerical simulation, to provide a scientific basis for the town and major infrastructure to defense the large-scale disasters caused by debris flow blocking river.Mainly for the following work and res-earch results have been achieved.(1) This paper studies the typical river-blocked case based on field surveys and literature data collection.The features of the river-blocked by debris flow are proposed.There are three river-blocked types:total blocking, obstruct blocking, and local blocking.Obstruct the potential dam blocking occurs mainly in high-velocity turbulent debris flow, or smaller bulk density viscous debris flow, whose characteristics are debris flow always move under the water, silts the riverbed, changes the river profile, and causes flooding disasters in the form of upstream backwater. Causing the river blockage in the form of barrier dam occurs mainly in viscous (or high concentration) debris flow.The main characteristics of partial blockage in the general situation are that barrier dam makes the flow become narrow, changes the channel, and affects the flood discharge capacity.But when block-up coefficient is greater than 0.8, the debris flow push the water flow, which can cause the different bank erosion.Debris flow total blocking event is not common,but once occ-urred,barrier lake will cause upstream flood disaster,dam-break will cause downstream extraordinary flood, even make the main river diversion in the wide valley segment which causes the serious disaster in a bigger range.(2) In the Minjiang River, most of events are partially damming the main river as a barrier dam. Using flume experiments, reappears blocking larger-iver by debris flow with high density viscous debris flow when intersection angle is 90 degrees. Reveals the characteristics of the process of debris flow into the main rivers and the mechanism of blocking the main river. Focus on the features of partially blocking the main river as a barriers dam, The exp-erimental results shows that the thrust force of the follow-up debris flow is a main dynamic force driving the debris flow in the main river; Total volume of debris flows has important effects on damming large river, which become serious with the volume of debris flow increasing; In the process of debris flow blocking river, when damming coefficient R increasing, velocity of main river firstly increases and then decreases, when R less than 0.8, the lost material of debris flow is very little, head-water level is increasing linearly; When R more than or equal to 0.8, the lost material of debris flow become serious, head-water level is increasing exponentially.(3) Based on the dynamic equation of the debris flow at different slo-pes,water and sediment dynamic processes,and the interaction between ba-rriers dam of debris flow and main river were considered,and a model of the runout distance of debris flow in big river was established.In view of the phenomenon that the material erosion is very serious when debris flowing into big river,the erosion coefficient is obtaineding using the test dates of flume experiment.Based on the total amount equation of debris flow was blocking given by Bifan ZHOU,a modal of the total amount of the big river blocked by debris flow was considered in hight of the erosion coefficient. The criterion of debris flow blocking big river waspresented in terms of dynamic process and total amount of debris flow.(4) Based on the importance of the blocking coefficient R for forecast-ting hazard and the model test data, the expressions of blocking coefficient R is derived, which can be used to estimate the degree of debris flow barrier dam blocking the river, and also as another criterion of partial blocking river by debris flow.(5) According to the characters of the submerged disk, the equation of the head-water level is given by the broad-crested weir theory.the equation for describing the movement of debris flow head is derived based on density current theory; Carries out univariate analysis on the affecting factors of the movement of debris flow head, the analysis show that the debris flow visc-osity and shear stress have no significant effect on the velocity of the debris flow head, and the coefficient of circle resistance is the greatest;The relat-ionship is established between the runout distance of debris flow head in big large river and time, on this basis, the formula of the minimum amount of solids material is given when submerged dam blocks the river.(6) According to the disaster mode of debris flow barrier dam blocking the river.The flow field of the main river with different block coefficients was analyzed by the numerical simulation method according to this disaster type. The order degree of the main river was studied based on information entropy principle. When the block coefficient R was in the range of 0.8 to 0.9, the entropy of the main river decreased rapidly, and the velocity of the water flow was fast. The block coefficient, R>0.80, was taken as the criterion of the local blocking of the river by the debris flow.Verified by the river-blocked event caused by the debris flow along Minjiang River between Yinxing to Yingxiu section, the results of numerical simulation compared with the field data well. The criterion of the disaster at the opposite bank due to river-blocked caused by the debris flow is validated. Then proposed block diagram of the criterion and flows debris effect.The equation of calculate the value of head-water level is given, which propose a method for calculate the value of scopes of back up water level.(7)For disaster effects of different modes of blocking the river,approp-riate mitigation countermeasures are proposed. For total blocking mode,ele-vating the line elevation in submerged area should be first considered. If subjected to other conditions it cannot be implemented, consider limiting the flow rate and total amount of debris flow into the main river, in order to reduce or eliminate debris flows blocking rivers. According to the partly damming main river, the main disaster is erosion the different bank, the main engineering measures to protect the bank are diversion project and support structure and so on, to the obstruct blocking just consider raising the line elevation.更多还原