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鱼脊型水石分离系统对漂木减灾效果的实验研究
Alternative TitleExperimental study on the mitigation effect of the herringbone water-sediment separation system for driftwood disaster
Language中文
谢湘平
Thesis Advisor韦方强
2014
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name硕士
Degree Discipline建筑与土木工程
Keyword山地灾害 漂木 鱼脊型水石分离系统 优化设计
Abstract在植被覆盖良好的山区,由于滑坡、沟岸侵蚀、风力、火灾等各种原因产生的枯、倒树木进入沟道、河流形成丰富的漂木,漂木是山地生态系统的重要组成。漂木既有重要的生态环境效应,也会产生严重的灾害效应,当山洪、泥石流携带漂木向下游运动时,会造成沟道桥涵堵塞,造成洪水泛滥;堵塞坝体,造成泥沙堆积;冲击建构筑物,造成严重破坏等。因此,对漂木灾害进行防治是山地灾害减灾的重要内容之一。 鱼脊型水石分离系统作为一种新型泥石流减灾结构,利用重力作用将泥石流中的较大砾石分离出来,同时也可将漂木分离出来,用于漂木灾害减灾。本文首先根据该系统的特点及漂木的危害性,确定了针对漂木的减灾策略,即“防堵增排、水木分离”;通过实验验证了该系统在合理的优化设计条件下能对漂木起到良好的减灾效果;并从结构本身及减灾对象两方面考虑,探讨了影响减灾效果的主要因素;最后提出了基于漂木减灾效果的结构参数优化设计原则。通过以上研究,取得了如下研究成果: 1、漂木易在引流坝前堆积,堵塞引流口,影响减灾效果。通过模型实验和现场考察,确定了漂木在引流坝前的堵塞堆积形态,主要呈三种:引流口搭桥型、交错咬合型、坝前停积型,其中,以引流口搭桥型堵塞最为普遍。 2、通过模型实验,确定了漂木在坝前堆积堵塞与漂木长度L和引流口宽度b之间的关系。漂木拦截率Pt随L/b的增大呈线性增大,而漂木堵塞率Pc在L/b<1时,变化不大,整体不超过5%,在坝口基本不堵塞;1肋梁坡度θ>相对跨度B/b>肋梁间隙a。漂木形态、漂木量及漂木流速等都会对结构的减灾效果产生一定的影响。 5、根据模型实验结果提出了基于漂木减灾效果的鱼脊型水石分离系统两大主要组成部分引流坝和水石分离格栅主要结构参数的优化方法。引流坝引流口开口宽度满足b/L>(0.5~1)时能起到较好的防堵增排效果。水石分离格栅各结构参数中,格栅跨度B、肋梁坡度θ主要以泥石流分离效果最佳的方法来取值;格栅长度M需考虑漂木速度的影响,在泥石流最优条件下乘以适当的速度放大系数;肋梁间隙a满足a<3.85D时能保证80%以上的漂木分离率;肋梁倾角γ则综合泥石流及漂木两者的分离效果和结构稳定性等因素综合取值,建议取或90°为最佳。 本文通过模型实验验证了鱼脊型水石分离系统具有良好的水木分离功能,并对影响水木分离效果的各因素进行了研究,提出了优化设计方法,为漂木减灾提供了一种有效的新手段。
Other AbstractIn mountain areas with forest coverage, there are full of fallen and dead woods due to landslide, bank erosion, windthrow, fire and disease or human activity. When these fallen woods are brought into streams and channels, they will become driftwoods. Driftwood is benefit to aquatic creatures and has positive effects on river morphology and hydrology from ecological perspective. When they go to the passive effects, they could cause severe damage to bridges, culverts and artificial channels, etc. due to their clog and accumulation in piers, aggravating erosion around piers, blocking freeboard, rising back water pressure. Driftwoods transported by debris flow or flood could form temporary dams which will amplify the peak discharge when they break out. Driftwoods often deposit and capture extra sediments in dams of debris flow defense. These sediments will reduce the service life of dams. Hence, it is of great importance and necessity to develop effective measures to reduce driftwood disasters in mountain disaster mitigation. Herringbonewater-sediment separationsystem, a new measure against debris flow disaster, invented very recently, is still in developing and testing stage. Its water-sediment separation function has been verified to be effective for debris flow by a series of model experiments. Can it also be used in driftwood defense? In order to answer this question, firstly, a series experiments were carried out to test the driftwood mitigation effects, which should a positive results. Secondly, efforts were taken to find out factors which significantly influence the mitigation effect,both from the structure characteristics and driftwood properties. At last, an optimal design method of the main structural parameters were proposed based on the driftwood mitigation effect. According to these researchs, following results are taken out. 1.As driftwood transported to the check dam, it accumulated and clogged in front of the dam and open spaces such as spillway. There are three main regimes of accumulation and clogging in or next to spillway, which are spillway bridging, muti-debris interacting and dead-water area depositing respectively. Among the three, spillway bridging is the most comman type found in nature. 2. Model tests results show that driftwood accumulation in front of drain dyke or clog in spillway have great relation with the relative log length(L/b). Driftwood accumulation rate increase linearly with the increase of L/b,while driftwood clogging rate keeps lower than 5% when L/b<1 and presents a parabola trend with L/b increase when 1
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/7829
Collection山地灾害与地表过程重点实验室
Recommended Citation
GB/T 7714
谢湘平. 鱼脊型水石分离系统对漂木减灾效果的实验研究[D]. 北京. 中国科学院研究生院,2014.
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