唐家山堰塞湖库区(北川～禹里段)地震地质灾害触发效应研究
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摘要
"5.12"大地震具有震级高、破坏性强、次生地质灾害严重的特点。通过地震前后对唐家山堰塞湖库区为中心的沿通口河北川~禹里段地震地质灾害现场地质调查,显示崩塌、滑坡和泥石流数量分别由地震前的5、3、0变为地震后的7、51、10个(条),地质灾害发育密度和模数分别由地震前的0.26个/km、46×104m3/km变为地震后的1.35个/km、104×104m3/km,地震后发育密度及模数分别是地震前的5.19和2.24倍,地震产生的边坡破坏效应极为显著。通过分段剖析,得出以下认识:1)距离发震断裂越近,地质灾害发育密度越高,就北川~禹里段沿通口河两岸岸坡而言,发震断裂上盘3 km范围是地震地质灾害的极(强)发育区,3~6 km范围为中等发育区,6~20km范围为弱发育区,20 km以外基本不受地震影响;2)地震地质灾害主要发育在顺向岸坡以及斜向~顺向岸坡结构内,且以大型和特大型滑坡为特征,常常发生堵江事件;而在逆向坡及斜向~逆向岸坡结构内地震地质灾害总体不发育,即使有也以崩塌为主,且主要发生在单薄山脊以及地形坡度陡峭处;3)地震对大型松散堆积体等整体复活主要受控于其地形坡度及微地貌特征,地形坡度40°以上以及由缓变陡的转折部位是古滑坡等松散堆积体整体或局部容易被地震触发失稳的充分条件,并非所有的古滑坡等松散堆积体均会被地震诱发而整体复活。
"5·12" Wenchuan large earthquake has the characteristics of high seismic magnitude,strong destructive,and serious secondary geological hazard.Through the field geological investigations of geohazards in Tang Jiashan dammed lake(Beichuan to Yuli) before and after the earthquake,it was found that the amount of rockfall,landslide,debris flow changed into 7,51,10 from 5,3,0 separately after earthquake;geohazards development density and modulus changed into 1.35 and 104 from 0.26 per kilometer and 460 thousand m3/km.The effecting of slope failure induced by earthquake was quite significant.Based on the field geological investigations and subsection analysis,the following recognitions were obtained which induced:1) The distance to triggering seismic fault is shorter and geohazards devel opment density is higher,as far as Tang Jiashan dammed lake(Beichuan to Yuli) is con-cerned,the earthquake geohazards development strongly within limits of 3 km distance to the hanging wall of triggering seismic fault,middle development within limits from 3 km to 6 km,weakly development within limits from 6 km to 20 km,it that the distance beyond 20 km has not influence.2) The earthquake geohazards mainly development in oblique~bedding bank slope and the geohazards mainly are large and huge landslide,and river blocking up happens frequently;the earthquake geohazards are no development in the whole in oblique~conversing bank slope,and the geohazards mainly are rockfall which mostly occur at thin mountain ridge and steep terrain.3) The whole reactivation of large accumulation body induced by earthquake is mainly controlled by terrain gradient and micro morphologic unit.Terrain gradien beyond 40° and turning position from gentle slope to steep slope are sufficient conditions for that old landslide or accumulation body wholely or locally losing stability induced by earthquake.
"5·12" Wenchuan large earthquake has the characteristics of high seismic magnitude,strong destructive,and serious secondary geological hazard.Through the field geological investigations of geohazards in Tang Jiashan dammed lake(Beichuan to Yuli) before and after the earthquake,it was found that the amount of rockfall,landslide,debris flow changed into 7,51,10 from 5,3,0 separately after earthquake;geohazards development density and modulus changed into 1.35 and 104 from 0.26 per kilometer and 460 thousand m3/km.The effecting of slope failure induced by earthquake was quite significant.Based on the field geological investigations and subsection analysis,the following recognitions were obtained which induced:1) The distance to triggering seismic fault is shorter and geohazards devel opment density is higher,as far as Tang Jiashan dammed lake(Beichuan to Yuli) is con-cerned,the earthquake geohazards development strongly within limits of 3 km distance to the hanging wall of triggering seismic fault,middle development within limits from 3 km to 6 km,weakly development within limits from 6 km to 20 km,it that the distance beyond 20 km has not influence.2) The earthquake geohazards mainly development in oblique~bedding bank slope and the geohazards mainly are large and huge landslide,and river blocking up happens frequently;the earthquake geohazards are no development in the whole in oblique~conversing bank slope,and the geohazards mainly are rockfall which mostly occur at thin mountain ridge and steep terrain.3) The whole reactivation of large accumulation body induced by earthquake is mainly controlled by terrain gradient and micro morphologic unit.Terrain gradien beyond 40° and turning position from gentle slope to steep slope are sufficient conditions for that old landslide or accumulation body wholely or locally losing stability induced by earthquake.
引文
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[2]Huang Runqiu.Characteristics of geological disasters of“5.12”Wenchuan earthquake and recommendation on its im-pact on reconstruction[J].Chinese Geological Education,2008,(2):21-24.[黄润秋,李为乐.“5.12”汶川大地震地质灾害的基本特征及其对灾后重建影响的建议[J].中国地质教育,2008,(2):21-24.]
[3]黄润秋,许强.中国典型灾难性滑坡[M].北京:科学出版社,2008.
[4]Huang Runqiu.Large-scale landslides and their slidingmechanisms in china since the 20th century[J].ChineseJournal of Rock Mechanics and Engineering,2007,26(3):433-454.[黄润秋.20世纪以来中国的大型滑坡及其发生机制[J].岩石力学与工程学报,2007,26(12):433-454.]
[5]Hu Xiewen,Huang Runqiu,Shi Yubing,et al.Analysis onblocking river mechanism of Tangjiashan landslide and dam-breaking mode of its barrier dam[J].Chinese Journal ofRock Mechanics and Engineering,2009,28(1):181-189.[胡卸文,黄润秋,施裕兵,等.唐家山滑坡堵江机制及堰塞坝溃坝模式分析[J].岩石力学与工程学报,2009,28(1):181-189.]
[6]Hu Xiewen,Shi Yubing,Lv Xiaoping,et al.Study report ofthe bank stability in Tangjiashan dammed lake and its down-stream[R].Chengdu:Southwest Jiaotong University,2009.[胡卸文,施裕兵,吕小平,等.唐家山堰塞湖库区及下游岸坡稳定性研究报告[R].成都:西南交通大学,2009.]
[7]Li Haoran,Hang Li,Li Qingchun,et al.Study report ofTongkou river hydropower station primarily design,beichuansichuan(engineering geology)[R].Chengdu:ChengduHydroelectric Investigation and Design Institute,China Hy-dropower Consulting Group.[李浩然,黄莉,李青春,等.四川省北川羌族自治县通口河漩坪水电站初步设计研究报告(工程地质)[R].成都:中国水电顾问集团成都勘测设计研究院,2006.]
[8]Deng Jianhui,Chen Fei,Yin Hu,et al.Geological originand stability evaluation of siwancun landslide in ludingcounty[J].Chinese Journal of Rock Mechanics and Engi-neering,2007,26(10):1 945-1 950.[邓建辉,陈菲,尹虎,等.泸定县四湾村滑坡的地质成因与稳定评价[J].岩石力学与工程学报,2007,26(10):1 945-1 950.]
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