芦山地震触发大岩崩滑坡-碎屑流特征与运动过程
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摘要
"4·20"芦山强烈地震次生地质灾害以崩塌、落石为主,滑坡较不发育,且规模小.但在天全县老场乡大庙村大岩崩却形成了地震灾区唯一一处大规模滑坡:在地震作用下,沿大岩崩单薄山脊两侧各约35.2万和42.0万m3的强风化白云质灰岩岩体高位、高速滑出,分别沿两侧高速运动,左、右侧沿途分别滑行约504和740 m后与各自主沟道形成撞击爬坡,在春尖窝沟左岸和干沟头主沟右岸爬高分别约35和26 m.随后又各自顺沟而下(沿春尖窝沟滑行763 m,沿干沟头沟滑行409 m),并在干沟头沟撞击点下游409 m处交汇,交汇后由于坡道较缓运动约223 m后停止,在主沟和春尖窝沟各形成8 000和600 m3的小堰塞湖,沿沟因无保护对象而未造成人员和财产损失.在对滑坡现场进行详细地质调查的基础上,结合现场测绘、勘探等手段,对大岩崩滑坡体的基本特征进行了较深入的研究,对滑坡发生及成灾原因进行了初步分析.结果表明,滑源区陡峭单薄山脊的地形条件、风化破碎的白云质灰岩岩体和有利的结构面组合是滑坡发生的基本条件;芦山7.0级地震对滑源区的震动效应是滑坡发生的直接诱因.
The secondary geological disasters triggered by "4·20" Lushan strong earthquake were dominated by rockfalls rather than landslides,and their scales were not large.However,there was a large-scale landslide in Damiao Village,Laochang Township,Tianquan County,the only large-scale landslide in the disaster area.There were about 35.2×104 and 42.0×104 m3 strongly weathered dolomitic limestone sliding out quickly from high places along both sides of thin ridge in Dayanbeng mountain,moving along grooves on both sides with a high speed,then sliding about 504 and 740 m respectively along the left and right ditches,hitting with their main channels and climbing about 35 and 26 m respectively in the left bank of Chunjianwo ditch and the right bank of Gangoutou main ditch.Afterwards they slid about 763 and 409 m respectively and intersected 409 m away from the impact point in Gangoutou ditch,then they slid about 223 m because of gentle slopes to form two small dammed lakes with volumes of 8 000 and 600 m3,causing no casualties and property loss because of no inhabitants along the ditch.On the basis of detailed geological survey and combining with field mapping,prospecting and other means,the basic features of Dayanbeng landslide were researched thoroughly,and the causes of the landslide were analysed preliminarily.The research result shows that the thin ridge,weathered dolomitic limestone and favorable structures are the basic conditions of the landslide,and vibration effect of "4·20" Lushan earthquake is the direct cause of the landslide.
The secondary geological disasters triggered by "4·20" Lushan strong earthquake were dominated by rockfalls rather than landslides,and their scales were not large.However,there was a large-scale landslide in Damiao Village,Laochang Township,Tianquan County,the only large-scale landslide in the disaster area.There were about 35.2×104 and 42.0×104 m3 strongly weathered dolomitic limestone sliding out quickly from high places along both sides of thin ridge in Dayanbeng mountain,moving along grooves on both sides with a high speed,then sliding about 504 and 740 m respectively along the left and right ditches,hitting with their main channels and climbing about 35 and 26 m respectively in the left bank of Chunjianwo ditch and the right bank of Gangoutou main ditch.Afterwards they slid about 763 and 409 m respectively and intersected 409 m away from the impact point in Gangoutou ditch,then they slid about 223 m because of gentle slopes to form two small dammed lakes with volumes of 8 000 and 600 m3,causing no casualties and property loss because of no inhabitants along the ditch.On the basis of detailed geological survey and combining with field mapping,prospecting and other means,the basic features of Dayanbeng landslide were researched thoroughly,and the causes of the landslide were analysed preliminarily.The research result shows that the thin ridge,weathered dolomitic limestone and favorable structures are the basic conditions of the landslide,and vibration effect of "4·20" Lushan earthquake is the direct cause of the landslide.
引文
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[3]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.HU Xiewen,HUANG Runqiu,SHI Yubing,et al.Analysis of blocking river mechanism of Tangjiashanlandslide and dam-breaking mode of its barrier dam[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(1):181-189.
[4]胡卸文,罗刚,黄润秋,等.唐家山滑坡后壁残留山体震后稳定性研究[J].岩石力学与工程学报,2009,28(11):2349-2359.HU Xiewen,LUO Gang,HUANG Runqiu,et al.Studyof stability of remnant mountain body in back scarp ofTangjiashan landslide after“5.12”Wenchuan earth-quake[J].Chinese Journal of Rock Mechanics andEngineering,2009,28(11):2349-2359.
[5]许强,裴向军,黄润秋.汶川地震大型滑坡研究[M].北京:科学出版社,2009:1-51.
[6]胡卸文,罗刚,王军桥,等.唐家山堰塞体渗流稳定及溃决模式分析[J].岩石力学与工程学报,2010,29(7):1409-1417.HU Xiewen,LUO Gang,WANG Junqiao,et al.Seepage stability analysis and dam-breaking mode ofTangjiashan barrier dam[J].Chinese Journal of RockMechanics and Engineering,2010,29(7):1409-1417.
[7]许强,董秀军,邓茂林,等.2010年7.27四川汉源二蛮山滑坡-碎屑流特征与成因机理研究[J].工程地质学报,2010,18(5):609-622.XU Qiang,DONG Xiujun,DENG Maolin,et al.TheErmanshan rock slide-debris flow of July 27,2010 inHanyuan,Sichuan:characteristics and failuremechanism[J].Journal of Engineering Geology,2010,18(5):609-622.
[8]黄润秋,裴向军,李天斌.汶川地震触发大光包巨型滑坡基本特征及形成机理分析[J].工程地质学报,2008,16(6):730-741.HUANG Runqiu,PEI Xiangjun,LI Tianbin.Basiccharacteristics and formation mechanism of the largestscale landslide at Dagungbao occurred during theWenchuan earthquake[J].Journal of EngineeringGeology,2008,16(6):730-741.
[9]GATTINONI P,SCESI L,ARIENI L,et al.TheFebruary 2010 large landslide at Maierato,ViboValentia,Southern Italy[J].Landslides,2012,9(2):255-261.
[10]HAVENITH H B,BOURDEAU C.Earthquake-induced landslide hazards in mountain regions:areview of case histories from central Asia[J].Geologica Belgica,2010,13(3):137-151.
[11]程谦恭,胡厚田,胡广韬,等.高速岩质滑坡临床弹冲与峰残强降复合启程加速动力学机理[J].岩石力学与工程学报,2000,19(2):173-176.CHENG Qiangong,HU Houtian,HU Guangtao,et al.A study of complex acceleration dynamics mechanismof high-speed landslide by elastic rocky impulse andpeak-residual strength drop[J].Chinese Journal ofRock Mechanics and Engineering,2000,19(2):173-176.
[12]程谦恭,胡厚田.剧冲式高速滑坡全程动力学机理分析[J].水文地质工程地质,1999(4):19-23.CHENG Qiangong,HU Houtian.Dynamical analysison the whole process of acute colliding high speedlandslide[J].Hydrogeology and Engineering Geology,1999(4):19-23.
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