IMHE OpenIR  > 山地灾害与地表过程重点实验室
泥石流对大型沟道松散堆积体的侵蚀机理研究
Alternative TitleStudy on the mechanics of debris flow entraining large-scale loose accumulation along the channel
李浦
Subtype博士
Thesis Advisor胡凯衡
2017
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline岩土工程
Keyword泥石流 侵蚀机理 松散堆积体 侵蚀率 泥石流演算模型
Abstract地震或震后强降雨等自然因素会引发一系列的崩塌、滑坡活动,使泥石流沟道存在大量的松散堆积体,这些松散物质改变了原有的沟床纵剖面形态。泥石流侵蚀松散物质组成的沟床时,会引起沟道形态的变化,同时放大自身规模,增大下游峰值泥石流流量和最大冲出距离,从而影响泥石流事件的灾害泛滥范围。本论文在野外调查的基础上,以典型泥石流灾害为原型,凝练研究模态,综合运用理论分析、水槽实验和数值计算的方法,对不同沟道纵剖面形态下泥石流的侵蚀特征和动床演算模型进行了探索,得到的主要研究成果如下:1、通过搜集资料、野外实地考察等手段对典型泥石流灾害进行详细分析,获取开展模型实验以及理论分析所需要的原型资料。揭示了泥石流沟道两种主要的基底侵蚀类型以及侵蚀深度的沿程分布特征,由此提炼泥石流沟道纵剖面形态原型。2、得到了沟道松散体纵剖面凹凸点处泥石流的侵蚀规律。根据弗洛德相似准则,考虑模型试验的尺度相似和动力学相似,提出了模型实验的初步设计。根据水槽实验的结果,在前人研究的基础上,得到沟道纵剖面由陡变缓和由缓变陡两种情形下的侵蚀率计算方式。拟合时R2值均接近于0.7,说明拟合得到的公式与实验结果较为吻合,能较好的反映凹凸点处侵蚀特征。3、根据沟道地形坡度是否是均一的,将沟道形态分为三种:均一坡度沟道、凹形沟道和凸形沟道。现场调查和实验现象揭示了变坡条件下两种典型的泥石流底床侵蚀方式:剪切侵蚀和冲击侵蚀。在Medina等人的研究基础上,利用力学分析和理论推导的方法,得到凹凸形态变坡沟道中综合的泥石流侵蚀率计算公式,并根据泥石流动床水槽实验的结果,确定公式中的待定参数。4、利用典型的河床演变计算模型(简称Cao模型)、泥石流动床演算模型(Hsu模型)以及新的侵蚀率计算模型(简称Hu模型),计算得到泥深、速度和侵蚀深度的沿程分布,并水槽实验结果进行对比分析,发现Cao、Hsu模型计算结果与实验结果相差很大,而Hu模型结果与实验测量结果较为吻合。然后以文家沟泥石流为实际沟道演算案例,通过改变沟道的平均坡度和剖面局部曲率,对比分析Medina模型和Hu模型的数值计算结果,发现沟道纵剖面为凹凸组合形态时Hu模型更加适用。5、根据泥石流水槽实验,得到了坡度不连续沟床经泥石流侵蚀后纵剖面形态的演化特征。由实验观察和分析可知,凸转折点附近在侵蚀过程中逐渐被“平滑”化;凹转折点附近的侵蚀具有明显的冲击侵蚀特性。侵蚀后纵剖面起伏也与沟床转折角有关,当转折角较小时,水力侵蚀为主,侵蚀后纵剖面起伏较小,当转折角增大时,重力侵蚀逐渐增强,出现局部的小崩塌或滑坡,侵蚀后沟道纵剖面起伏增大。最后利用小波工具对侵蚀后底床形态进行了分析。
Other AbstractLandslides and avalanches induced by seismic shaking and post-seismic intense rainfalls produce plentiful loose material in debris flow channels. The abrupt deposition of loose material in the channel changes the original bed morphology, resulting in an irregular distribution of inflexion points. Debris flow entraining mobile material can change the channel morphology, enhance its own scale and increase the downstream debris flow peak discharge and the maximum run-out distance, thus affecting the disaster flooding area. Based on field investigation, this paper takes the typical debris flow disaster as the prototype, synthetically used theoretical analysis, model experiments and numerical simulation to explore the characteristics of the debris flow erosion. A model for debris flow routing along channel was developed. The main research conclusions are as follows:1 Through the collection of survey data, field investigation of typical debris flow events for a detailed analysis, we obtain the required prototype data for model experiments and the theoretical analysis. Analyzing the main types of erosion and its spatial distribution, the prototypical longitudinal profile of debris flow is extracted. 2 The erosion characteristics of the debris flow at concave and convex sites of the channel are studied. According to the similarity criterion of Freud, considering the similarity and dynamic similarity of the model test, the preliminary design of the model experiment is put forward.Based on the results of flume experiments and previous studies, the erosion rate formula for debris flowing over concave and convex points is obtained. The values of fitting coefficient R2 are close to 0.7, indicating that the fitted formulas are in good agreement with experimental results.3 According to whether the channel gradient is uniform, the channel shape is divided into three kinds: uniform, concave and convex channel. Field investigations and experimental phenomenas reveal two types of debris flow entrainment in slope-changing channels: shear erosion and impact erosion. Based on the study of Medina, we deduced the formula for calculating the erosion rate of debris flow by means of mechanics analysis and theoretical derivation. According to the results of flume experiments, the parameters is determined.4 The distribution of flow depth, velocity and erosion depth is calculated by using a typical riverbed evolution calculation model (Cao model), debris flow bed calculus model (Hsu model) and the new erosion rate calculation model (referred to as Hu model) , and the results of the flume were compared and analyzed. Then, taking the Wenjia Torrent debris flow as the actual channel calculation, the numerical results of the Medina model and the Hu model are compared and analyzed by changing the average slope and the local curvature of the channel.5 According to the experiment of debris flow, the evolution characteristics of longitudinal profile are discussed. We found that in concave sections, the inflexion points were gradually smoothed and headward erosion seems quite weak, while in convex sites obvious impact erosion was detected with rather deep erosion hole. The topographic relief of post-experiment bed profile also correlated with inflexion points. Small transition angles implies lower relief where the erosion process is dominated by hydraulic erosion. When transition angle grows, mass erosion intensified and landslides and avalanches emerges on a small scale, generating higher relief in the post-experiment bed profile. Finally, the shape of the bed after erosion is analyzed by using the wavelet tool.
Pages120
Language中文
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/24582
Collection山地灾害与地表过程重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
First Author Affilication中国科学院水利部成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
李浦. 泥石流对大型沟道松散堆积体的侵蚀机理研究[D]. 北京. 中国科学院大学,2017.
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