5·12地震后灾区泥石流危险度增加系数评价
摘要
5.12地震不仅直接引发了大量的崩塌、滑坡,而且降低流域内岩土体的强度,使其更易于受到侵蚀,从而为泥石流的形成提供丰富的固体物质。灾区震后泥石流活动频繁,并造成了较大的损失。泥石流沟的危险度评价是进行灾后重建的必要条件。选择震后固体物质增加量、地震烈度和堰塞坝规模这3个重要参数,提出了基于泥石流设计流量的震后泥石流危险度增加系数的评价方法。该方法通过计算地震后新增加的固体物质方量与通过配方法计算出的一次泥石流冲出物总量的比值,该比值与地震烈度影响系数的乘积及堰塞体蓄水量以流域50年一遇的流量排泄所需要时间3项之和来表达地震后泥石流危险度增加量。经灾区9条典型泥石流沟谷的计算验证,该方法做为一种新的方法,可快速、准确地评价5.12地震后灾区泥石流危险度的增加情况。
Wenchuan Earthquake not only induced a large amount of collapses and landslides immediately,but also reduced the strength of rock and soil mass in drainage basin,which makes them to be eroded more easily,so that abundant solid matter is provided for the formation of debris flows.The occurrence of debris flow is frequent in the disaster area after the earthquake and great losses have been caused.Evaluation on the risk degree of debris flow ditches is a necessary condition for post-disaster reconstruction.Three important parameters,i.e.,increment of solid matter,seismic intensity,and scale of barrier dam,are selected and evaluation method on increase coefficient of debris flow risk degree after earthquake is put forward based on designed debris flow.In this method,increase of debris flow risk degree is expressed by the ratio of added volume of solid matter to gross obtruding matter in a debris flow,seismic intensity multiplying the ratio,and time(hour)needed to drain water body in barrier dam with P_50% flux of the valley.By the validation of calculation for 9 typical debris flow ditches in the disaster area,the increase of debris flow risk degree in the May 12th disaster area after earthquake can be assessed by the new method,rapidly and precisely.
Wenchuan Earthquake not only induced a large amount of collapses and landslides immediately,but also reduced the strength of rock and soil mass in drainage basin,which makes them to be eroded more easily,so that abundant solid matter is provided for the formation of debris flows.The occurrence of debris flow is frequent in the disaster area after the earthquake and great losses have been caused.Evaluation on the risk degree of debris flow ditches is a necessary condition for post-disaster reconstruction.Three important parameters,i.e.,increment of solid matter,seismic intensity,and scale of barrier dam,are selected and evaluation method on increase coefficient of debris flow risk degree after earthquake is put forward based on designed debris flow.In this method,increase of debris flow risk degree is expressed by the ratio of added volume of solid matter to gross obtruding matter in a debris flow,seismic intensity multiplying the ratio,and time(hour)needed to drain water body in barrier dam with P_50% flux of the valley.By the validation of calculation for 9 typical debris flow ditches in the disaster area,the increase of debris flow risk degree in the May 12th disaster area after earthquake can be assessed by the new method,rapidly and precisely.
引文
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[2]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.
[3]钟敦伦.试论地震在泥石流活动中的作用[C]∥第一届全国泥石流学术会议论文集.1980.
[4]Shieh C L,Chen Y S,Tsai Y J,et al.Variability in rainfall threshold for debris flowafter the Chi-Chi earth-quake in central Tai wan,China[J].International Journal of Sediment Research,2009,24(2):177-188.
[5]陈俞旭.地震对崩塌与土石流发生的影响之研究[D].台湾:成功大学,2008.
[6]陈宁生,崔鹏,王晓颖,等.地震作用下泥石流源区砾石土体强度的衰减实验[J].岩石力学与工程学报,2004,23(16):2743-2747.
[7]刘希林.我国泥石流危险度评价研究:回顾与展望[J].自然灾害学报,2002,11(4):1-8.
[8]马鹏里,蒲金涌,辛吉武.甘肃省长江流域大(暴)雨引发泥石流危险程度评价[J].水土保持通报,2007,27(5):67-70.
[9]谢洪,钟敦伦,矫震,等.2008年汶川地震重灾区的泥石流[J].山地学报,2009:501-509.
[10]陈宁生,黄蓉,李欢,等.汶川5.12地震次生泥石流沟应急判识方法与指标[J].山地学报,2009:108-114.
[11]唐川,铁永波.汶川震区北川县城魏家沟暴雨泥石流灾害调查分析[J].山地学报,2009:625-630.
[12]谢洪,王士革,孔纪名.“5.12”汶川地震次生山地灾害的分布与特点[J].山地学报,2008,26(4):396-401.
[13]崔鹏,韦方强,陈晓清,等.汶川地震次生山地灾害及其减灾对策[J].中国科学院院刊,2008,23(4):317-323.
[14]Chen NS,Yang C L,Zhou W,et al.The critical rain-fall characteristics for torrents and debris flows in the Wenchuan earthquake stricken area[J].Journal of Mountain Science,2009,6(4):362-372.
[15]Tang C,Zhu J,Li WL,et al.Rainfall-triggered deb-ris flows following the Wenchuan earthquake[J].Bulle-tin of Engineering Geology and the Environment,2009,68(2):187-194.
[16]国家防汛抗旱指挥部办公室,中国科学院水利部成都山地灾害与环境研究所.山洪泥石流滑坡灾害及防治[M].北京:科学出版社,1994.
[17]张金山,沈兴菊,谢洪.低频泥石流特征及防治:以四川汶川县茶园沟为例[J].中国地质灾害与防治学报,2005,16(3):37-41.
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