唐家山堰塞坝“9·24”泥石流堵江及溃决模式
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摘要
"5·12"汶川地震导致唐家山高速滑坡堵江,形成唐家山堰塞湖.经过6月10日正常泄流后,堰塞坝体右岸还存在唐家山残留山体稳定性以及附近大水沟、小水沟泥石流等潜在危害.现场实地调查显示,受地震影响,大水沟、小水沟及无名沟沟域内崩塌和滑坡发育,形成了极为丰富的松散物源,具备发生坡面和沟谷泥石流的所有条件,也成为唐家山堰塞湖成功泄水后,仍对堰塞湖正常利用起控制作用的严重地质灾害隐患点之一,"6·14"和"9·24"2次大规模泥石流又导致通口河分别堵江断流4和17h.在查明唐家山堰塞体右岸3条冲沟内松散物源分布及稳定性的基础上,重点结合"9·24"泥石流发育状况,对大水沟、小水沟和无名沟泥石流的发育特征及其动力学特性,尤其是在不同降雨频率下一次冲出泥石流时唐家山堰塞坝体泄水槽的堵江状况及溃决模式进行了系统分析.分析结果表明:3条冲沟形成泥石流堵江后,一次全溃决的可能性很小,其溃决模式为"扇缘部位首先过流→水流挤压左岸并淘刷左岸堰塞体→逐级冲开堆积扇".这一模式对震后地震灾区泥石流的研究具有指导和借鉴意义.
"5·12" Wenchuan earthquake caused a high-speed landslide on the Tangjiashan mountain to block the Tongkou river to form the Tangjiashan dammed lake. After a normal discharge on June 10,2008,there were potential hazards of stability loss of remnant Tangjashan mountain body and debris flows in Dashui and Xiaoshui ditches on the right bank of Tangjashan barrier dam. Through an on-the-spot investigation,due to the effect of the earthquake collapses and landslides developed in Dashui,Xiaoshui and Wuming ditches to form extremely rich loose sources,having all conditions of slope and valley debris flows. That become one of the potential serious dangers of geological disasters after the Tangjiashan dammed lake had been successfully discharged and controlled the normal use of the Tangjiashan dammed lake. "6·14" and "9·24" debris flows,two large-scale debris flows occurring respectively on June 14 and September 24,2008,made the Tongkou river blocked respectively for 4 and 17 h. Based on identifying the distribution and stability of loose sources in the three ditches on the right bank of the Tangjiashan barrier dam and importantly by combining the developmental situation of "9·24" debris flow,the developmental and dynamic features of the three ditches,especially the river-blocking situation at discharge spout of the Tangjiashan barrier dam and breaking mode when the three ditches break out debris flows at the same time under different rain frequencies,were analyzed systematically. The research result shows that the possibility that debris fans break once completely is very small after debris flows block the river,and the breaking mode is that firstly flood flows over the edge of debris fans,secondly crushes and scours the left of the barrier body,finally rushes out debris fans gradually. This mode provides a guidance and reference for the research on debris flow in the disaster areas after the Wenchuan earthquake.
"5·12" Wenchuan earthquake caused a high-speed landslide on the Tangjiashan mountain to block the Tongkou river to form the Tangjiashan dammed lake. After a normal discharge on June 10,2008,there were potential hazards of stability loss of remnant Tangjashan mountain body and debris flows in Dashui and Xiaoshui ditches on the right bank of Tangjashan barrier dam. Through an on-the-spot investigation,due to the effect of the earthquake collapses and landslides developed in Dashui,Xiaoshui and Wuming ditches to form extremely rich loose sources,having all conditions of slope and valley debris flows. That become one of the potential serious dangers of geological disasters after the Tangjiashan dammed lake had been successfully discharged and controlled the normal use of the Tangjiashan dammed lake. "6·14" and "9·24" debris flows,two large-scale debris flows occurring respectively on June 14 and September 24,2008,made the Tongkou river blocked respectively for 4 and 17 h. Based on identifying the distribution and stability of loose sources in the three ditches on the right bank of the Tangjiashan barrier dam and importantly by combining the developmental situation of "9·24" debris flow,the developmental and dynamic features of the three ditches,especially the river-blocking situation at discharge spout of the Tangjiashan barrier dam and breaking mode when the three ditches break out debris flows at the same time under different rain frequencies,were analyzed systematically. The research result shows that the possibility that debris fans break once completely is very small after debris flows block the river,and the breaking mode is that firstly flood flows over the edge of debris fans,secondly crushes and scours the left of the barrier body,finally rushes out debris fans gradually. This mode provides a guidance and reference for the research on debris flow in the disaster areas after the Wenchuan earthquake.
引文
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[3]唐兴邦.中国泥石流[M].北京:商务印书馆,2000:246-295.
[4]陈洪凯,唐春梅,陈野鹰.公路泥石流研究及治理[M].人民交通出版社,2004:47-58.
[5]谢洪,钟敦伦,韦方强.我国山区城镇泥石流灾害及其成因[J].山地学报,2006,24(1):79-87.XIE Hong,ZHONG Dunlun,WEI Fangqiang.Debris flow hazards and their formation causes in mountain urban area of China[J].Journal of Mountain Science,2006,24(1):79-87.
[6]HUNGR O.Analysis of debris flow surges using the theory of uniformly progressive flow[J].Earth Surface Processes and Landforms,2000,25:483-495.
[7]IVERSON M,RCOSTN E J,LAHUSEN G R.Large-scale debris-flowflume becomes operational in Oregon[C]∥Landslide News.[s.l].:[s.n].,1993:29-30.
[8]TAMOTSU T.Debris flow[M].Rotterdam:A.A.Balkma,1991:26-89.
[9]张金山,沈兴菊,谢洪.泥石流堵河影响因素研究———以岷江上游为例[J].灾害学,2007,22(2):82-86.ZHANG Jinshan,SHEN Xingju,XIE Hong.Study on factors affecting the river-blocking due to debris-flow in the upper reaches of Minjiang River[J].Journal of Catastrophology,2007,22(2):82-86.
[10]刘希林,唐川.泥石流危险性评价[M].北京:科学出版社,1995:84-91.
[11]王裕宜,胡凯衡.泥石流体的流变和冲淤特征及其与危险度的关系[J].自然灾害学报,2007,16(1):17-22.WANG Yuyi,HU Kaiheng.Relationship between rheology/erosion-deposit properties of debris flow and its hazard degree[J].Journal of Natural Disasters,2007,16(1):17-22.
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