汶川县渔子溪地震地质灾害特征及灾害链成生分析
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摘要
渔子溪下游耿达乡-映秀镇河段是汶川地震触发震害最为严重、灾害链效应最为显著的河段之一。本文通过详细的实地调查和遥感影像分析,力求揭示该河段地质灾害的特征及灾害链的成生过程、成生条件。依据震害特征,将地质灾害划分为斜坡中上部强风化岩土体失稳坠落、块状岩质边坡滑移式垮塌及局地暴雨启动型泥石流3类,并分析震害发育规律。调查表明,灾害点的空间展布受控于发震断裂,且北岸发育密度更大,茂汶断裂两侧差异显著。对51个崩塌点及17条泥石流研究发现,地震崩塌灾害主要发生在40°以上斜坡,主要分布在斜坡中上部(0.4倍坡高以上)及地貌突出部位,且大纵比降的壮年期沟谷易发泥石流。同时,诱发因素的转变致使地质灾害向降雨主导的小规模单体崩塌、泥石流方向发展。区内主要存在2种地质灾害链:(1)内动力地质灾害链"地震→崩塌→压迫河道、毁路或形成堰塞湖",其成生过程经历高速启动、滑移运动、堵河3个阶段;(2)内外动力耦合作用地质灾害链"地震→崩塌、震裂山体→暴雨→泥石流→压迫河道、毁路或形成堰塞湖",成生过程可划分为启动、堵塞(沟谷后)溃决、铺床、堵河4个阶段。灾害链的成生条件概括为:脆弱的地质环境;强烈地震动震垮、震裂高陡斜坡(>50m,>40°);强降雨及适宜的堵河条件。
Under the influence of 5.12 earthquake,the geo-hazards are extreme serious in the reach of the Yuzi Stream form Gengda to Yingxiu.The geo-hazard chains are also very prominent.Through field investigation and remote sensing interpretation,this paper tries to reveal the characteristics and genetic process and conditions of geologic hazards in the stream.Based on their characteristics,the geo-hazards are divided into three types.They are(1) instability and crash of the highly weathered rock-mass and soil on the upper slopes,(2) collapse of massive rock-mass slope,and(3) local downpour types of debris flows.The geo-hazards are controlled by seismic fault and the density is higher on the north shore.They show significant deviations between the two sides of Maowen fault zone.51 collapses and 17 debris flows are analyzed.The geo-hazards mainly took place on the slopes steeper than 40°.The instability positions are mainly upon the parts with slope gradients more than 0.4 and failure zones distribute on the upside of the slopes.Debris flows mainly occur in the valley of the large slope and manhood.The geo-hazards can be transformed into small-scale single collapses and debris flows induced by rainfall.There are mainly two types of geo-hazard chains:(1) geo-hazard chains due to inner dynamic-"earthquake → collapses → stream squeezed,road destroyed and the barrier lakes".The genetic process includes three stages: high-speed start,glide motion,stoppage;(2) geo-hazards chains due to the inner and outer dynamic coupling effect-"earthquake → collapses and shattered mountains → rainstorm →debris flows → stream squeezed,road destroyed and the barrier lakes".The genetic process can be divided into four parts: preparation,dam-breaking after the valley blocked,bed-making and stoppage.The genetic conditions of geo-hazard chains can be concluded as follows: vulnerable geology environment,high steep slope(>50m,>40°) collapsed and shattered by the strong ground motion,the heavy rainfall and suitable conditions for blocking the river.
Under the influence of 5.12 earthquake,the geo-hazards are extreme serious in the reach of the Yuzi Stream form Gengda to Yingxiu.The geo-hazard chains are also very prominent.Through field investigation and remote sensing interpretation,this paper tries to reveal the characteristics and genetic process and conditions of geologic hazards in the stream.Based on their characteristics,the geo-hazards are divided into three types.They are(1) instability and crash of the highly weathered rock-mass and soil on the upper slopes,(2) collapse of massive rock-mass slope,and(3) local downpour types of debris flows.The geo-hazards are controlled by seismic fault and the density is higher on the north shore.They show significant deviations between the two sides of Maowen fault zone.51 collapses and 17 debris flows are analyzed.The geo-hazards mainly took place on the slopes steeper than 40°.The instability positions are mainly upon the parts with slope gradients more than 0.4 and failure zones distribute on the upside of the slopes.Debris flows mainly occur in the valley of the large slope and manhood.The geo-hazards can be transformed into small-scale single collapses and debris flows induced by rainfall.There are mainly two types of geo-hazard chains:(1) geo-hazard chains due to inner dynamic-"earthquake → collapses → stream squeezed,road destroyed and the barrier lakes".The genetic process includes three stages: high-speed start,glide motion,stoppage;(2) geo-hazards chains due to the inner and outer dynamic coupling effect-"earthquake → collapses and shattered mountains → rainstorm →debris flows → stream squeezed,road destroyed and the barrier lakes".The genetic process can be divided into four parts: preparation,dam-breaking after the valley blocked,bed-making and stoppage.The genetic conditions of geo-hazard chains can be concluded as follows: vulnerable geology environment,high steep slope(>50m,>40°) collapsed and shattered by the strong ground motion,the heavy rainfall and suitable conditions for blocking the river.
引文
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[11]陈日东,刘兴年,曹叔尤,郭志学.泥石流与主河汇流堆积的数值模拟[J].中国科学:技术科学,2011,41(10):1305～1314.Chen Ridong,Liu Xingnian,Cao Shuyou,Guo Zhixue.Numerical simulation of deposit in confluence zone of debris flowand mainstream.Science China,2011,41(10):1305～1314.
[12]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.Tang Chuan,Liang Jingtao.Characteristics of debris flows inBeichuan epicenter of the Wenchuan earthquake triggered byrainstorm on September 24,2008.Journal of EngineeringGeology,2008,16(6):751～758.
[13]韩金良,吴树仁,汪华斌.地质灾害链[J].地学前缘,2007,14(6):11～20.Han Jinliang,Wu Shuren,Wang Huabin.Preliminary study ongeological hazard chains.Earth Science Frontiers,2007,14(6):11～20.
[2]胡广韬,毛彦龙,程谦恭.地震时滑坡体波动振荡的启程加速动力学问题[R].西安:西安工程学院研究报告,1997,17～19.Hu Guangtao,Mao Yanlong,Cheng Qiangong.Acceleration Dy-namics on Fluctuations of Landslides During an Earthquake.Xi'an:Xi'an College of Engineering,1997,17～19.
[3]黄润秋.汶川地震地质灾害研究[M].北京:科学出版社,2010,2～6.Huang Runqiu.Geo-hazard Assessment of Wenchuan Earthquake.Beijing:Science Press,2010,2～6.
[4]孙进忠,陈祥,王余庆.岩土边坡地震崩滑的三级评判预测[J].地震研究,2004,27(3):256～264.Sun Jinzhong,Chen Xiang,Wang Yuqing.The estimation andprediction of the slide and collapse of soil and rock triggered byearth-quakes with three steps.Journal of Seismological Research,2004,27(3):256～264.
[5]贺可强,安振远.崩滑碎屑流的形成条件与形成类型[J].河北地质学院学报,1996,19(3/4):344～351.He Keqiang,An Zhenyuan.A preliminary analysis on the formingcondition and forming type of debris flow caused by landslide sandfalls.Journal of Hebei College of Geology,1996,19(3/4):344～351.
[6]程强,吴事贵,苏玉杰.映秀-卧龙公路沿线汶川地震地质灾害研究[J].工程地质学报,2010,18(2):160～167.Cheng Qiang,Wu Shigui,Su Yujie.Gelogical hazards due toWenchuan earthquake along Yingxiu to Wolong highway.Journalof Engineering Geology,2010,18(2):160～167.
[7]王全才,王兰生,李宗有,王浩.“5.12”汶川地震区都汶路老虎嘴崩塌体治理[J].山地学报,2010,28(6):132～139.Wang Quancai,Wang Lansheng,Li Zongyou,Wang Hao.Reme-diation of Laohuzui rockfall in Duwen road induced by Wenchuan“5.12”earthquake.Journal of Mountain Science,2010,28(6):132～139.
[8]张倬元,王士天,王兰生.工程地质分析原理[M].北京:地质出版社,1997,93～97.Zhang Zhuoyuan,Wang Shitian,Wang Lansheng.Principle ofEngineering Geological Analysis.Beijing:Geological PublishingHouse,1997,93～97.
[9]许强.四川省8.13特大泥石流灾害特点、成因与启示[J].工程地质学报,2010,18(5):597～607.Xu Qiang.The 13 August 2010 catastrophic debris flows inSichuan province:Characteristics,genetic mechanism and sugges-tion.Journal of Engineering Geology,2010,18(5):597～607.
[10]胡明鉴,汪稔,陈中学,王志兵.泥石流启动过程PFC数值模拟[J].岩土力学,2010,31(增1):395～433.Hu Mingjian,Wang Nian,Chen Zhongxue,Wang Zhibing.Initi-ation process simulation of debris deposit based on particle flowcode.Rock and Soil Mechanics,2010,31(Suppl.1):395～433.
[11]陈日东,刘兴年,曹叔尤,郭志学.泥石流与主河汇流堆积的数值模拟[J].中国科学:技术科学,2011,41(10):1305～1314.Chen Ridong,Liu Xingnian,Cao Shuyou,Guo Zhixue.Numerical simulation of deposit in confluence zone of debris flowand mainstream.Science China,2011,41(10):1305～1314.
[12]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.Tang Chuan,Liang Jingtao.Characteristics of debris flows inBeichuan epicenter of the Wenchuan earthquake triggered byrainstorm on September 24,2008.Journal of EngineeringGeology,2008,16(6):751～758.
[13]韩金良,吴树仁,汪华斌.地质灾害链[J].地学前缘,2007,14(6):11～20.Han Jinliang,Wu Shuren,Wang Huabin.Preliminary study ongeological hazard chains.Earth Science Frontiers,2007,14(6):11～20.
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