汶川地震后四川安县甘沟堵溃泥石流及其对策
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摘要
汶川地震诱发的大量崩塌和滑坡不仅直接为泥石流活动提供松散固体物质,还可能造成沟道堵塞。沟道内的堵塞坝虽然不像主河道上的堰塞湖那样造成大范围灾害,但溃决后却会引发大规模泥石流,给人民生命财产和基础设施等造成严重危害。以四川省安县高川乡甘沟为例,说明其造成泥石流的危害特征及防治对策。通过对甘沟自然环境背景条件的分析,发现甘沟具备泥石流暴发的地形地貌和降水条件;流域内地震诱发的崩滑体不仅为泥石流的形成提供丰富的松散固体物质,还造成沟道堵塞,形成堵溃型泥石流。甘沟已建的排导槽存在过流能力不够、槽底和侧墙已基本被破坏、弯道处未考虑超高、沟内未布置拦挡工程等问题。目前沟内由于松散固体物质充足,在一定的降水条件下,仍会再次暴发泥石流。针对甘沟的具体情况,提出了修建拦挡、重建排导槽并结合预警预报措施的防治对策,并对重建排导槽的过流断面进行了优化设计。
A large number of landslides,induced by the Wenchuan Earthquake,directly provide loose materials for subsequent debris flows,but also may cause channel blockage.Channel blockage,as contrasted with river blockage,may not cause widespread damages,but it will transform into large-scale debris flows and cause serious harm to people's lives and property and infrastructure.In this paper,taking Gangou gully of Anxian County in Sichuan Province of China as example,we studied the debris flow characteristics and put forward the control debris flow measures.Based on analysis of the natural environment conditions in the gully,we found that its topography was prone to form debris flows.According to the remote sensing interpretation,there was a big landslide,approximately 0.45 million m3 in volume,induced by the earthquake,blocking the channel and forming a landslide dam.It was the failure of the dam that formed large-scale debris flows and caused serious damages to local people.It was also found that the drainage canal had no enough flow capacity and the canal basement and side walls had been destroyed and the excess-height in bend of the drainage canal had not been taken into account.Additionally,there was no debris dam and check dam in the gully.Unfortunately,under the condition of rainfall,debris flows will occur again due to enough loose solid materials in the gully.To solve these problems,the countermeasures of building check dams,heightening drainage canal,warning and forecasting were put forward in this paper.Especially,we considered the optimal cross-section characteristics of debris flow drainage canal in the gully.
A large number of landslides,induced by the Wenchuan Earthquake,directly provide loose materials for subsequent debris flows,but also may cause channel blockage.Channel blockage,as contrasted with river blockage,may not cause widespread damages,but it will transform into large-scale debris flows and cause serious harm to people's lives and property and infrastructure.In this paper,taking Gangou gully of Anxian County in Sichuan Province of China as example,we studied the debris flow characteristics and put forward the control debris flow measures.Based on analysis of the natural environment conditions in the gully,we found that its topography was prone to form debris flows.According to the remote sensing interpretation,there was a big landslide,approximately 0.45 million m3 in volume,induced by the earthquake,blocking the channel and forming a landslide dam.It was the failure of the dam that formed large-scale debris flows and caused serious damages to local people.It was also found that the drainage canal had no enough flow capacity and the canal basement and side walls had been destroyed and the excess-height in bend of the drainage canal had not been taken into account.Additionally,there was no debris dam and check dam in the gully.Unfortunately,under the condition of rainfall,debris flows will occur again due to enough loose solid materials in the gully.To solve these problems,the countermeasures of building check dams,heightening drainage canal,warning and forecasting were put forward in this paper.Especially,we considered the optimal cross-section characteristics of debris flow drainage canal in the gully.
引文
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[2]Li Yong,Huang Runqiu,Zhou Rongjun,et al.Geological back-ground of Longmen Shan Seismic Belt and surface ruptures in Wen-chuan earthquake[J].Journal of Engineering Geology,2009,17(1):3-18[李勇,黄润秋,周荣军,等.龙门山地震带的地质背景与汶川地震的地表破裂[J].工程地质学报,17(1):3-18]
[3]Xu Xiwei,Wen Xueze,Ye Jianqing,et al.The Ms 8.0 Wenchuanearthquake surface ruptures and its seismogenic structure[J].Seis-mology and Geology,2008,30(3):597-629[徐锡伟,闻学泽,叶建青,等.汶川Ms8.0地震地表破裂带及其发震构造[J].地震地质,2008,30(3):597-629]
[4]Zhou Rongjun,Huang Runqiu,Lei Jiancheng,et al.Surface rup-ture and hazard characteristics of Wenchuan earthquake with Magni-tude8.0 in Sichuan Province[J].Chinese Journal of Rockmechan-ics and Engineering,2008,27(11):2173-2183[周荣军,黄润秋,雷建成,等.四川汶川8.0级地震地表破裂与震害特点[J].岩石力学与工程学报,2008,27(11):2173-2183]
[5]Tang Chuan,Liang Jingtao.Characteristics of debris flows in Bei-chuan epicenter of the Wenchuan earthquake triggered by rainstormon September 24,2008[J].Journal of Engineering Geology,2008,16(6):751-758[唐川,梁京涛.汶川震区北川9.24暴雨泥石流特征研究[J].工程地质学报.2008,16(6):751-758]
[6]Lin C W.Impact of Chi-Chi earthquake on the occurrence of land-slides and debris flows:example fromthe Chenyulan River watershed,Nantou,Taiwan[J].Engineering Geology,2003,(71):49-61
[7]Zhou Bifan,Li Deji,Luo Defu,et al.Guide to Prevention of DebrisFlow[M].Beijing:Science Press,1991:125-129[周必凡,李德基,罗德富,等.泥石流防治指南[M].北京:科学出版社,1991:125-129]
[8]You Yong,Liu Jinfeng,Chen Xingzhang.A convenient designationfor the optimal hydraulic cross-section of“Rectangle-V”shapeddrainage canal of viscous debris flow[G]//Edited by Harold Anne-garn,IGARSS 2009-International Geoscience and Remote SensingSymposium,Cape Town,South Africa,07-2009,II392-395
[9]You Yong.Optimal hydraulic condition of debris flowdrainage canal[J].Journal of Mountain Science,1999,17(3):255-258[游勇.泥石流排导槽水力最佳断面[J].山地学报,1999,17(3):255-258]
[10]You Yong,Liu Jinfeng.Comparison of hydraulics conditions amongusual debris flow drainage canal[J].Chinese Journal of Rock Me-chanics and Engineering,2006,25(Suppl.1):2820-2825[游勇,柳金峰,欧国强.泥石流常用排导槽水力条件的比较[J].岩石力学与工程学报,2006,25(Suppl.1):2820-2825]
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