再论大光包滑坡特征与形成机制
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摘要
大光包滑坡是汶川地震触发的规模最大的巨型滑坡。滑坡位于安县高川乡、汶川地震发震断裂上盘,滑动距离4.5km,堆积体宽度2.2km,面积7.8km2,估算体积7.5亿m3。与地震灾区178处特大滑坡相比,大光包滑坡除了强震触发崩滑灾害具有的震动溃裂、溃滑失稳、超强动力和大规模高速抛射与远程运动等特征之外,还存在一个长度大于lkm的长大滑面,是其余滑坡绝无仅有的!作者在2008年研究的基础上,又多次到现场调查、测绘并取样分析,初步认为大光包滑坡发生过程为一次性完成,滑带物质组成较为复杂,主体为震旦系(Zd)风化程度较高的泥质灰岩,局部夹泥盆系沙窝子组(Ds)磷矿及其伴生矿。滑坡形成机理主要分为以下4个阶段:即(1)坡体震裂阶段:在强震作用下后缘拉裂边界及上游拉裂边界形成,并与下游侧的岩层层面构成巨大的"V"型楔形体;(2)滑面碎裂化,摩阻力急剧降低阶段:滑坡下游边界(主控滑动面)滑床被震裂、松弛、剪胀-扩容并碎裂化,产生滚动摩擦效应,导致滑面摩阻力急剧降低;(3)前部"锁固段"剪断,高速溃滑阶段:滑体前部滑面上的锁固段在强震持续作用下,产生突发性剪断,从而导致整个巨大的楔形体,如同"拉抽屉"一样,沿岩层走向高速溃滑而下;(4)震动堆积阶段:滑体冲过黄洞子沟,受到迎面山体的强力阻挡,逆冲爬高500余m后,表部惯性极大的松散岩土体快速折返并震动堆积、荡平,余势不减的碎屑流汇入滑坡扩容抛撒体,向黄洞子沟下游流动1km,止于大偏桥。
Daguangbao landslide in Gaochuan town Anxian county is located on the upper plate of the CausativeFault of wenchuan earthquake. Its slide distance is 4.5 km, and its maximum width of accumulation is 2. 2 km. Thearea is 7.8 km2 , and estimated volume is 750 million m3. It is the largest landslide among individual landslides trig-gered by Wenchuan earthquake. Comparing with the other 178 large landslides in earthquake disaster area, Da-guangbao landslide has the same characteristics as falls and slide disaster triggered by strong earthquake. They in-clude shake debacle, unstability of debacle and slide mechanism, super-dynamic characteristics, large-scale andhigh-speed projectile, and long-distance movement. But it has itself standout trait, namely, a long-large sliding sur-face more than 1 km long and 100 ～250 m wide,which is in a class by itself. On the basis of the study last year,the author has further progressed the site investigation many times, and has finished mapping and sampling analysis.The preliminary view is that Daguangbao landslide occurring process is one-time completion. Composition of sliding zone is very complex. It is mainly composed of stronger weathering argillaceous limestone of Sinian, and its part stratum contains Devonian shawozi sub-group ( Ds) and its associated phosphate ore. Its formation mechanism can be divided into the following 3 stages. (1) Stage of slope shattering cracking. Rear fracturing boundary and upstream fracturing boundary were shaped under strong earthquake, and they composed huge wedge " V" with downstream rock beddings. (2) Stage of friction sharply decrease and slope shattering-sliding. Sliding bed at downstream bound-ary (the main controlling sliding surface) began shattering-cracking, relaxation, cutting expand-bulk enlarge. Stroll-ing scrape effect made the friction decrease sharply, and made the huge wedge slide with high speed along bedding strike, like "pulling drawer". (3) Stage of shattering-sliding—shaking-accumulating. Landslide body rushed into Hongdongzi gully and was barred strongly by faced mountain, so it thrust up more than 500 m, and then its surficial loose accumulation with large inertia began fastly backing and shaking, accumulating, shaking level. Debris flows whose inertia force did not decrease imported landslide and enlarged ejection body. At last,it stopped at Dapianqiao bridge after flowing 1 km towards downstream of Hongdongzi gully.
Daguangbao landslide in Gaochuan town Anxian county is located on the upper plate of the CausativeFault of wenchuan earthquake. Its slide distance is 4.5 km, and its maximum width of accumulation is 2. 2 km. Thearea is 7.8 km2 , and estimated volume is 750 million m3. It is the largest landslide among individual landslides trig-gered by Wenchuan earthquake. Comparing with the other 178 large landslides in earthquake disaster area, Da-guangbao landslide has the same characteristics as falls and slide disaster triggered by strong earthquake. They in-clude shake debacle, unstability of debacle and slide mechanism, super-dynamic characteristics, large-scale andhigh-speed projectile, and long-distance movement. But it has itself standout trait, namely, a long-large sliding sur-face more than 1 km long and 100 ～250 m wide,which is in a class by itself. On the basis of the study last year,the author has further progressed the site investigation many times, and has finished mapping and sampling analysis.The preliminary view is that Daguangbao landslide occurring process is one-time completion. Composition of sliding zone is very complex. It is mainly composed of stronger weathering argillaceous limestone of Sinian, and its part stratum contains Devonian shawozi sub-group ( Ds) and its associated phosphate ore. Its formation mechanism can be divided into the following 3 stages. (1) Stage of slope shattering cracking. Rear fracturing boundary and upstream fracturing boundary were shaped under strong earthquake, and they composed huge wedge " V" with downstream rock beddings. (2) Stage of friction sharply decrease and slope shattering-sliding. Sliding bed at downstream bound-ary (the main controlling sliding surface) began shattering-cracking, relaxation, cutting expand-bulk enlarge. Stroll-ing scrape effect made the friction decrease sharply, and made the huge wedge slide with high speed along bedding strike, like "pulling drawer". (3) Stage of shattering-sliding—shaking-accumulating. Landslide body rushed into Hongdongzi gully and was barred strongly by faced mountain, so it thrust up more than 500 m, and then its surficial loose accumulation with large inertia began fastly backing and shaking, accumulating, shaking level. Debris flows whose inertia force did not decrease imported landslide and enlarged ejection body. At last,it stopped at Dapianqiao bridge after flowing 1 km towards downstream of Hongdongzi gully.
引文
[1]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 Xianjun,Li Tianbin.The Basic Characteristics and Formation Mechanism of Daguangbao Large-scale Landslide triggered by Wenchuan Earthquake.Journal of Engineering Geolo-gy,2008,16(6):730～741.
[2]殷跃平.汶川八级地震滑坡触发特征研究[J].工程地质学报,2009,17(1):29～38.Yin Yueping.Features of landsl ides triggered by thewenchuan earth2quake.Journal of Engineering Geology,2009,17(1):29～38.
[3]王治华,徐起德,徐斌,张微.5.12汶川地震航空遥感应急调查[J].中国科学E辑:技术科学,2009,39(7):1304～1311.Wang zhihua et al..Aerial remote sensing investigation of5.12Wenchuan Earthquake.Journal of China Science E:Technology Science,2009,39(7):1304～1311.
[4]黄润秋.汶川地震触发地质灾害机理及其地质力学模式[J].岩石力学与工程学报,2009,28(06):882～891.Huang Runqiu Mechanism and Geomechanical models of landslides triggered by Wenchuan Earthquake,Chinese Journal of Rock Me-chanics and Engineering.2009,28(06):882～891.
[5]黄润秋.中国典型灾难性滑坡[M].北京:科学出版社,2008,131～132.Huang Runqiu.Catastrophic landsldide in China.Beijing:Science Press,2008,131～132.
[6]查小刚.断层是洒勒山滑坡的基础:水和土体重力是它的决定因素[J].水土保持通报,1983,(3),27～33.Zha Xiaogang.Fault is basic of Saleshan landslide:the determinant is water and soil gravity.Journal of Water and Soil Conservation,1983,(3):27～33.
[7]伍超等.雅砻江唐古栋垮山堵江溃决洪水过程研究[J].水动力学研究与进展,1996,A辑,11(6):646～652.Wu Chao.et al..Hydrograph of the Dam-breakflood ofthe reser-voir form ed by mountMn collapse in Yalongiiang.Joumal of Hydro-dynamies,1996,A,11(6):646～652.
[8]王兰生等,Diexi Earthquake-Landslide and its environmenton the Upstream of Min River of Sichuan(叠溪地震滑坡和环境)[R],POSTER presentation(Code:A32IGGEKAR),32届世界地质大会展板成果,2004年7月,意大利,都灵.Wang Lansheng.Diexi Earthquak e-Landslide an d its environ-ment on the Upstream of Min River of Sichuan,POSTER presenta-tion(Code:A32IGGEKAR),July,2004.Italy,Turin.
[9]中华人民共和国地质图说明书(比例尺:1:50000)清平幅[S].四川省地质矿产局化探队,1995年11月.Geological map specificaton of the People S Republic of China(Scale:1:50000),Qingping serial.Geochemical exploration bri-gade of geology&mineral resources exploration&development bu-reau of Sichuan,Nov.1995.
[10]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,1994.Zhang Zhuoyuan,Wang Shitian,Wang Lanheng.Principles of engi-neering geological analysis.Beijing:Geological Publishing House,1994.
[2]殷跃平.汶川八级地震滑坡触发特征研究[J].工程地质学报,2009,17(1):29～38.Yin Yueping.Features of landsl ides triggered by thewenchuan earth2quake.Journal of Engineering Geology,2009,17(1):29～38.
[3]王治华,徐起德,徐斌,张微.5.12汶川地震航空遥感应急调查[J].中国科学E辑:技术科学,2009,39(7):1304～1311.Wang zhihua et al..Aerial remote sensing investigation of5.12Wenchuan Earthquake.Journal of China Science E:Technology Science,2009,39(7):1304～1311.
[4]黄润秋.汶川地震触发地质灾害机理及其地质力学模式[J].岩石力学与工程学报,2009,28(06):882～891.Huang Runqiu Mechanism and Geomechanical models of landslides triggered by Wenchuan Earthquake,Chinese Journal of Rock Me-chanics and Engineering.2009,28(06):882～891.
[5]黄润秋.中国典型灾难性滑坡[M].北京:科学出版社,2008,131～132.Huang Runqiu.Catastrophic landsldide in China.Beijing:Science Press,2008,131～132.
[6]查小刚.断层是洒勒山滑坡的基础:水和土体重力是它的决定因素[J].水土保持通报,1983,(3),27～33.Zha Xiaogang.Fault is basic of Saleshan landslide:the determinant is water and soil gravity.Journal of Water and Soil Conservation,1983,(3):27～33.
[7]伍超等.雅砻江唐古栋垮山堵江溃决洪水过程研究[J].水动力学研究与进展,1996,A辑,11(6):646～652.Wu Chao.et al..Hydrograph of the Dam-breakflood ofthe reser-voir form ed by mountMn collapse in Yalongiiang.Joumal of Hydro-dynamies,1996,A,11(6):646～652.
[8]王兰生等,Diexi Earthquake-Landslide and its environmenton the Upstream of Min River of Sichuan(叠溪地震滑坡和环境)[R],POSTER presentation(Code:A32IGGEKAR),32届世界地质大会展板成果,2004年7月,意大利,都灵.Wang Lansheng.Diexi Earthquak e-Landslide an d its environ-ment on the Upstream of Min River of Sichuan,POSTER presenta-tion(Code:A32IGGEKAR),July,2004.Italy,Turin.
[9]中华人民共和国地质图说明书(比例尺:1:50000)清平幅[S].四川省地质矿产局化探队,1995年11月.Geological map specificaton of the People S Republic of China(Scale:1:50000),Qingping serial.Geochemical exploration bri-gade of geology&mineral resources exploration&development bu-reau of Sichuan,Nov.1995.
[10]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,1994.Zhang Zhuoyuan,Wang Shitian,Wang Lanheng.Principles of engi-neering geological analysis.Beijing:Geological Publishing House,1994.
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