重庆小南海地震崩滑体的基本特征及形成机制研究
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摘要
通过对重庆小南海地震崩滑堆积体进行野外地质调查和工程地质勘察等相关工作,阐述了该崩滑堆积体的基本特征和形成机制,认为其形成过程经历了"风化剥蚀→震荡抛射→崩滑堆积→堵江成湖"4个阶段,其岩体破坏形式为高度破裂或严重高度破裂状态,其岩体破坏过程以崩塌为主,滑动为辅。研究发现,小南海地震崩滑堆积体的最终形成是受地震构造运动及应力、岩体构造、地形地貌及地震波作用等因素综合作用的结果:(1)该区NE向黔江逆滑(右行)断裂与NNW向仰头山逆滑(左行)断层形成的"X"型地震构造组合及轴向呈NWW向的构造压应力使小南海断块内部发生张滑(左行)破裂而导致61/4级地震发生;(2)该区呈"X"形展布的3组主要构造节理是崩滑体发育的物质基础,大、小垮岩在地震波作用下最终发生了向山体临空面(约145°~155°方向)的各自崩滑;(3)从崩滑堆积体中发现的灰岩块石证明崩滑体原始地层中曾含二叠系栖霞组和茅口组灰岩,这为恢复崩滑前山体地形提供了直接证据;(4)崩滑体中堆积岩块直径分布区域沿约150°方向自WN到ES依次递减,间接证明了地震时崩滑体抛洒方向为约150°方向,且大、小垮岩分别形成堆积区,交叉堆积部分较少。
This paper presents the field geological investigation,engineering geological exploration and other related studies on the collapsed and slided debris mass induced by the Xiaonanhai Earthquake in Chongqing city.Basic characteristics and formation mechanism of the debris mass are elaborated.It is held that the forming process of the mass consists of four steps: namely weathering and denudation,shocking and projecting,collapse-slide accumulating and dammed lake formation.Collapses rather than landslides appeared in process of rock mass fracturing and rock blocks in accumulation body are quite and even more fragmental.Research shows that the mass is a result of comprehensive actions including seismotectonic moving and stress field,rock mass structure,topography and geomorphology,and seismic wave.First of all,the left lateral tensile-slip fracture in Xiaonanhai fault block was induced by X-shaped seismotectonic combination.It consists of the NE trending right lateral Qianjiang reverse-slip fracture and the NNW trending left lateral Yangtoushan reverse-slip fault.The NWW trending axially tectonic compression resulted in the M61/4 earthquake.Secondly,the rock mass near both Dakuayan and Xiaokuayan with three groups of tectonic joints forming X-shape collapsed respectively towards their free faces,at about 145°~155° direction.Thirdly,the limestone rubbles discovered in the collapse-slide mass prove that mountain body before moving contains limestone belong Qixia and Maokou formations during the Permian period.This discovery provides the evidence for restoring mountain body before its collapse-slide.Finally,the diameter of rock blocks in accumulation body decreases from northwest to southeast along 150° direction.I It proves indirectly that the direction of rock mass ejecting is along 150o direction.What's more,the collapse-slide masses from mountain body near Dakuayan and Xiaokuayan form their accumulation bodies,respectively.Therefore their overlapping part is small.
This paper presents the field geological investigation,engineering geological exploration and other related studies on the collapsed and slided debris mass induced by the Xiaonanhai Earthquake in Chongqing city.Basic characteristics and formation mechanism of the debris mass are elaborated.It is held that the forming process of the mass consists of four steps: namely weathering and denudation,shocking and projecting,collapse-slide accumulating and dammed lake formation.Collapses rather than landslides appeared in process of rock mass fracturing and rock blocks in accumulation body are quite and even more fragmental.Research shows that the mass is a result of comprehensive actions including seismotectonic moving and stress field,rock mass structure,topography and geomorphology,and seismic wave.First of all,the left lateral tensile-slip fracture in Xiaonanhai fault block was induced by X-shaped seismotectonic combination.It consists of the NE trending right lateral Qianjiang reverse-slip fracture and the NNW trending left lateral Yangtoushan reverse-slip fault.The NWW trending axially tectonic compression resulted in the M61/4 earthquake.Secondly,the rock mass near both Dakuayan and Xiaokuayan with three groups of tectonic joints forming X-shape collapsed respectively towards their free faces,at about 145°~155° direction.Thirdly,the limestone rubbles discovered in the collapse-slide mass prove that mountain body before moving contains limestone belong Qixia and Maokou formations during the Permian period.This discovery provides the evidence for restoring mountain body before its collapse-slide.Finally,the diameter of rock blocks in accumulation body decreases from northwest to southeast along 150° direction.I It proves indirectly that the direction of rock mass ejecting is along 150o direction.What's more,the collapse-slide masses from mountain body near Dakuayan and Xiaokuayan form their accumulation bodies,respectively.Therefore their overlapping part is small.
引文
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[13]吴玮江,王念秦.黄土滑坡的基本类型与活动特征[J].中国地质灾害与防治学报,2002,13(2):36~40.Wu Weijiang,Wang Nianqin.Basic types and active features ofloess landslide.The Chinese Journal of Geological Hazard andControl,2002,13(2):36~40.
[14]丁仁杰,李克昌.重庆地震研究暨《重庆1:50万地震构造图》[M].北京:地震出版社,2004.Ding Renjie,Li Kechang.Study on earthquake in Chongqing city《1:500000 seismotectonic map in Chongqing city》.Beijing:Earthquake Publishing House.
[15]杨涛,邓荣贵,刘小丽.四川地区地震崩塌滑坡的基本特征及危险性分区[J].山地学报,2002,20(4):456~460.Yang Tao,Deng Ronggui,Liu Xiaoli.The distributing and sub-area character of the seismic landslides in Sichuan.Journal ofMountain Science,2002,20(4):456~460.
[16]刘衡秋,胡瑞林.大型复杂松散堆积体形成机制的内外动力耦合作用初探[J].工程地质学报,2008,16(3):291~297.Liu Hengqiu,Hu Ruilin.Coupling of earth′s endogenic and exo-genic geological processes on formation mechanismof large-scaleloose complex quaternary deposits in western China.Journal ofEngineering Geology,2008,16(3):291~297.
[17]杨继红,董金玉,等.某水电站库区堆积体边坡的成因机制分析及稳定性评价[J].工程地质学报,2008,16(3):311~318.Yang Jihong,Dong Jinyu,et al..Formation mechanism and sta-bility assessment of deposit slope located in reservoir region.Jour-nal of Engineering Geology,2008,16(3):311~318.
[2]胡聿贤.地震工程学.北京:地震出版社,1988.Hu Yuxian.Earthquake engineering.Beijing:Earthquake Pub-lishing House,1988.
[3]Richter C.F.Elementary seismology[M].San Francisco:W.H.Freeman and Co.,1958.
[4]Keefer D.V.Landslides caused by earthquakes[J].GeologicalSociety of America Bulletin,1984,95(4).
[5]Papadopoulos G.A.,and Plessa A.Magnitude-distance relationsfor earthquake-induced landslide in Greece[J].EngineeringGeology,Special Issue,2000,58(3~4).
[6]Prestininzi A.,and Romeo R.Earthquake-induced ground fail-ures in Italy[J].Engineering Geology,Special Issue,2000,58(3~4).
[7]Romeo R.Seismically induced landslide displacements:a predic-tive model[J].Engineering Geology,Special Issue,2000,58(3~4).
[8]Jibson R.W.,Harp E.l.and Michael J.A.Amethod for produ-cing digital probabilistic seismic landslide hazard maps[J].Engi-neering Geology,Special Issue,2000,58(3~4).
[9]张倬元,王士天,王兰生.工程地质分析原理[M].北京:科学出版社,1993.Zhang Zhuoyuan,Wang Shitian,Wang Lansheng.Principles ofengineering geology.Beijing:Science Press,1993.
[10]胡光韬.滑坡动力学[M].北京:科学出版社,1995.Hu Guangtao.Dynamic landslide.Beijing:Science Press,1995.
[11]许强,黄润秋.地震作用下结构非线性响应的突变分析[J].岩土工程学报,1997,19(4):25~29.Xu Qiang,Huang Runqiu.Catastrophic analysis of nonlinear re-sponse of structure under earthquake.Chinese Journal ofGeotechnical Engineering,1997,19(4):25~29.
[12]祁生文,伍法权,刘春玲,等.地震边坡稳定性的工程地质分析[J].岩石力学与工程学报,2004,23(16):2792~2797.Qi Shengwen,Wu Faquan,Liu Chunling,et al..Engineeringgeology analysis on stability of slope under earthquake.ChineseJournal of Rock Mechanics and Engineering,2004,23(16):2792~2797.
[13]吴玮江,王念秦.黄土滑坡的基本类型与活动特征[J].中国地质灾害与防治学报,2002,13(2):36~40.Wu Weijiang,Wang Nianqin.Basic types and active features ofloess landslide.The Chinese Journal of Geological Hazard andControl,2002,13(2):36~40.
[14]丁仁杰,李克昌.重庆地震研究暨《重庆1:50万地震构造图》[M].北京:地震出版社,2004.Ding Renjie,Li Kechang.Study on earthquake in Chongqing city《1:500000 seismotectonic map in Chongqing city》.Beijing:Earthquake Publishing House.
[15]杨涛,邓荣贵,刘小丽.四川地区地震崩塌滑坡的基本特征及危险性分区[J].山地学报,2002,20(4):456~460.Yang Tao,Deng Ronggui,Liu Xiaoli.The distributing and sub-area character of the seismic landslides in Sichuan.Journal ofMountain Science,2002,20(4):456~460.
[16]刘衡秋,胡瑞林.大型复杂松散堆积体形成机制的内外动力耦合作用初探[J].工程地质学报,2008,16(3):291~297.Liu Hengqiu,Hu Ruilin.Coupling of earth′s endogenic and exo-genic geological processes on formation mechanismof large-scaleloose complex quaternary deposits in western China.Journal ofEngineering Geology,2008,16(3):291~297.
[17]杨继红,董金玉,等.某水电站库区堆积体边坡的成因机制分析及稳定性评价[J].工程地质学报,2008,16(3):311~318.Yang Jihong,Dong Jinyu,et al..Formation mechanism and sta-bility assessment of deposit slope located in reservoir region.Jour-nal of Engineering Geology,2008,16(3):311~318.
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