不同来水来沙条件下山区河流的河床响应试验研究

发布时间：2018-01-24 00:40

本文关键词： 山区河流泥沙补给河床变形水位陡增水沙灾害　出处：《工程科学与技术》2017年S1期 　论文类型：期刊论文

【摘要】：山区河流受季节性水文条件及产沙过程的影响,水沙条件变化频繁。尤其是暴雨山洪频繁挟带大量泥沙进入河道,从而引起河床急剧调整。本文以龙溪河典型河段为研究对象,通过调查天然河道的地形、床沙组成及来水来沙特性,开展系列水沙模型试验,突出分析来水来沙条件变化的河床响应。试验包括不同流量下清水冲刷和恒定流量下改变泥沙补给条件两种对比方案。以泥沙起动条件的沙莫夫公式判定方法,分析比较了不同工况条件下的断面泥沙起动流速和水流运动平均流速的关系,揭示不同断面间泥沙冲淤特性及河床变形特点。在此基础上,探讨河道沿程水位变化及致灾范围,对比分析表明,龙溪河在清水来流条件下,即使通过最大流量300 m3/s,洪水位也未超过龙池镇堤防高程,即清水来流条件一般不会影响龙池镇的防洪安全。若大量泥沙下泄至主河道,龙池镇段由于河床比降变缓与河道展宽等床面形态的变化,水流平均流速显著降低,携沙能力减小,引起大量泥沙淤积,致使水位陡增,甚至出现漫滩现象,存在显著的防洪安全隐患。随着泥沙补给量的不断增加,河床不同区域输沙动力的调整制约了泥沙的输移距离,从而引起局部区域河床的淤堵,并导致洪水位的增加,甚至产生漫滩洪水并诱发洪水灾害。研究表明,山区河流泥沙补给对河床响应及水沙灾害具有重大的影响,来水来沙变化下的水沙运动致灾机理亟需深入研究。
[Abstract]:Influenced by the seasonal hydrological conditions and sediment yield, the water and sediment conditions change frequently in mountain rivers, especially the heavy rain torrential torrents frequently carry a large amount of sediment into the channel. This paper takes the typical reach of Longxi River as the research object, and carries out a series of water and sediment model tests by investigating the topography, the composition of bed sediment and the characteristics of incoming water and sediment. The experiment includes two contrast schemes: clean water scour under different flow rate and changing sediment recharge condition at constant flow. The method of determining sediment incipient condition by Shamoff formula is presented. The relationship between the initial velocity of sediment and the average velocity of water flow under different working conditions is analyzed and compared to reveal the characteristics of sediment scouring and silting and the characteristics of river bed deformation among different sections. In this paper, the variation of water level along the river course and the range of disasters are discussed. The comparative analysis shows that the flood water level of Longxi River does not exceed the elevation of Longchi Town embankment even though the maximum discharge is 300 m3 / s under the condition of clear water flow. If a large amount of sediment is released to the main river, the river bed shape of Longchi Town will change due to the slowing down of the river bed ratio and the widening of the river channel. The average velocity of flow decreased significantly, and the sediment carrying capacity decreased, resulting in a large amount of sediment deposition, resulting in a steep increase in water level, even the phenomenon of flooding, there are significant flood control safety risks, with the continuous increase of sediment supply. The adjustment of sediment transport power in different areas of river bed restricts the distance of sediment transport, thus causing the siltation of the river bed in some areas, and leading to the increase of flood water level, even causing floodplain flood and inducing flood disaster. Sediment recharge in mountain rivers has great influence on river bed response and flood and sediment disasters. The mechanism of water and sediment movement induced by changes of incoming water and sediment needs to be studied in depth.
【作者单位】：四川大学水力学与山区河流开发保护国家重点实验室水利水电学院;
【基金】：国家自然科学基金资助项目(51579163;51639007) 国家重点研发计划重点资助项目(2016YFC0402302)
【分类号】：TV14
【正文快照】： 山区流域暴雨山洪频发,并且响应时间短、水流速度高、冲击力大,会造成坡沟失稳破坏、坡体滑塌、沟床下切,同时挟带大量泥沙输送至河道下游。而山区流域水系发育丰富,河网密度大,河床比降变化剧烈,颗粒起动条件变化差异显著,致使泥沙在局部区域发生明显的淤堵,降低河流的排洪输

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