震区重力侵蚀及其产沙输沙效应研究——以震中牛圈沟为例
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摘要
震区重力侵蚀及其产沙输沙效应造成严重的水土流失、河道淤积和城镇损毁,极大地改变了灾区生态环境并严重威胁灾后恢复重建和重大工程安全,是目前国内外研究的热点问题。以汶川地震震中牛圈沟流域为研究区,在崩塌、滑坡、泥石流等重力侵蚀区布设野外监测网,选择流域中下游的典型部位,采用GPS、全站仪、3D激光扫描系统和GIS等现代测绘技术,进行不同水土条件下的坡面、断面、沟道和地表形变监测,分析泥石流等重力侵蚀的发育特征、产沙输沙效应和致灾能力。研究结果表明:1)泥石流具有大冲大淤特征,在流域中下游一场泥石流最大冲刷和淤积深度分别达6.84和4.77 m;2)在沟道上部,泥石流表现为冲刷特征,其中最大冲刷6.84 m;3)在沟道中部,前期泥石流会产生弯道超高现象,凹岸比凸岸平均高出2.2 m,在后期泥石流表现出大规模冲刷作用,最大冲刷深度3.77 m;4)在沟道下部,前期泥石流表现为堆积特征,平均堆积厚度达1.65 m,后期泥石流表现冲刷作用,河床向一侧迁移,并形成倾斜河床;5)重力侵蚀具有强烈的产沙输沙效应,一场泥石流的平均产沙输沙量和堆积厚度可达到15.2×104m3和1.44 m、最大输沙量和冲刷深度分别可达16.2×104m3和1.53 m。研究结果可以为灾区重大工程选址选线、河流整治和次生山地灾害防治工程设计提供依据和参考,对保障山区公共与生态安全具有重要意义。
Niujuangou gully,the epicenter of Wenchuan Earthquake,was taken as the study area and the field observation stations and sections were established in the typical zones of gravitational Erosion such as rockfall,landslide and debris flow.Modern surveying and mapping technologies including GPS,total station and 3D laser scanning system were adopted and field surveying of slope,section,channel and surface deformation were conducted on different geo-hazard bodies.The development feature and the sediment yield and transportation were analyzed.The results showed tha debris flow is the typical of strong erosion and giant deposit with the maximum respective erosion and siltation depth of 6.84 m and 4.77 m only once.In the upper reaches of channel,debris flow shows erosion features with the maximum erosion depth of 6.84 m,and in the middle reaches of channel,the preceding debris flow takes on the super-elevation in curve ways with 2.2 m higher in concave bank than in convex bank and the later-period debris flow displays large-scale erosion with the maximum scour depth of 3.77 m.In the lower reaches of channel,debris flow shows accumulation features with the mean deposition thickness of 1.65m.Gravitational erosion has a violent effect of sediment yield and transportation with the mean sediment yield volume and accumulation thickness of 15.2×104 and 1.44 m as well as the maximum sediment transportation volume and scour depth of 16.2×104 m3 and 1.53 m.The results can be used as references for location line selection of key projects,river regulation and control engineering optimization design of mountain hazards.
Niujuangou gully,the epicenter of Wenchuan Earthquake,was taken as the study area and the field observation stations and sections were established in the typical zones of gravitational Erosion such as rockfall,landslide and debris flow.Modern surveying and mapping technologies including GPS,total station and 3D laser scanning system were adopted and field surveying of slope,section,channel and surface deformation were conducted on different geo-hazard bodies.The development feature and the sediment yield and transportation were analyzed.The results showed tha debris flow is the typical of strong erosion and giant deposit with the maximum respective erosion and siltation depth of 6.84 m and 4.77 m only once.In the upper reaches of channel,debris flow shows erosion features with the maximum erosion depth of 6.84 m,and in the middle reaches of channel,the preceding debris flow takes on the super-elevation in curve ways with 2.2 m higher in concave bank than in convex bank and the later-period debris flow displays large-scale erosion with the maximum scour depth of 3.77 m.In the lower reaches of channel,debris flow shows accumulation features with the mean deposition thickness of 1.65m.Gravitational erosion has a violent effect of sediment yield and transportation with the mean sediment yield volume and accumulation thickness of 15.2×104 and 1.44 m as well as the maximum sediment transportation volume and scour depth of 16.2×104 m3 and 1.53 m.The results can be used as references for location line selection of key projects,river regulation and control engineering optimization design of mountain hazards.
引文
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[7]Cui Peng,He Yiping,Chen Jie.Debris flow sediment trans-portation and its effects on Rivers in Mountain Area[J].Journal of Mountain Science,2006(5):539-549.[崔鹏,何易平,陈杰.泥石流输沙及其对山区河道的影响[J].山地学报,2006(5):539-549.]
[2]Tamura T.Analysis of the relationship between the arealdistribution of earthquake-induced landslides and the earth-quake magnitudes[J].Geological Review of Japan,1978,662-672.
[3]Gao Zhenhuan,Zhu Shulian.Earthquake soil rook flow innagano in Japan[J].North China Earthquake Sciences,1986,4(5):53-59.[高振寰,朱淑莲.日本长野县的地震泥石流[J].华北地震科学,1986,4(5):53-59.]
[4]Jiang Bo,Yu Ketao,Dai Lisi.Earthquake-induced geologicalhazard and its forming environment in China[J].The Chi-nese Journal of Geological Hazard and Control,1991,2(1):16-24.[蒋溥,于克涛,戴丽思.中国地震地质灾害及其宏观成因环境[J].中国地质灾害与防治学报,1991(1):16-24.]
[5]Ma Dongtao.An approach on effects of earthquakes on for-mation of debris flow[J].Northwestern Seismological Jour-nal,1996,19(4):38-42.[马东涛.试论地震在泥石流形成中的作用[J].西北地震学报,1996,19(4):38-42.]
[6]Liu Chianan,Huang Hsiao-Fung,Dong Jia-Jyun.Impacts ofSeptember 21,1999 Chi-Chi earthquake on the characteris-tics of gully-type debris flows in central Taiwan[J].NatHazards,2008,47:349-368.
[7]Cui Peng,He Yiping,Chen Jie.Debris flow sediment trans-portation and its effects on Rivers in Mountain Area[J].Journal of Mountain Science,2006(5):539-549.[崔鹏,何易平,陈杰.泥石流输沙及其对山区河道的影响[J].山地学报,2006(5):539-549.]
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