宝兴县城周边4·20芦山强烈地震地质灾害触发效应
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摘要
四川省4·20芦山7.0级地震具有震级高、破坏性强等特点,地震次生地质灾害以崩塌落石为主,滑坡不发育.与汶川5.12特大地震诱发的次生地质灾害相比,无论规模还是数量均显示较轻,但是处于地震影响区的宝兴县城却是个例外,县城周边山体因地形陡峻,表现出崩、滑灾害发育的特点.通过地震前、后对宝兴县城周边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3、1、3个(条)变为地震后的21、1、3个(条);地质灾害发育密度和模数分别由地震前的0.38个/km、0.34万m3/km变为地震后的2.02个/km、5.59万m3/km;地震后发育密度及模数分别是地震前的5.3和16.4倍;地震产生的边坡破坏效应显著.在此基础上,通过分段剖析可知:地震地质灾害主要发生在单薄山脊以及地形坡度陡峭处,岩质边坡以崩塌落石为主,松散层边坡则以滑坡为特征,但大型滑坡少见;地震对处于斜坡地带(非单薄山脊部位)大型松散堆积体等整体复活很少,只是局部陡缓交界部位存在坍滑或震动裂缝,整体稳定性较好,说明强震并不一定会诱发古滑坡等大型松散堆积体的整体复活.
Even though Lushan 4·20 strong earthquake has characteristics of high seismic magnitude and strong destructiveness,its secondary geological disasters are dominated by rockfalls rather than landslides.Compared with secondary geological disasters induced by 5·12 Wenchuan earthquake,their size and number are both mild.However,Baoxing County,which is in the earthquake-affected zone,is an exception.Rockfalls and landslides develop well around the county because of steep mountains.Geological field investigations of the geohazards around Baoxing County before and after the earthquake show that after earthquake the number of rockfall,landslide and debris flood changes into 21,1,and 3 from 3,1,and 3,respectively;geohazards development density and modulus change into 2.02 km-1 and 5.59×104 m3/km from 0.38 km-1 and 3.4×103 m3/km,respectively,which are 5.3 and 16.4 times that before the earthquake;and the effect of slope failure induced by the earthquake is significant.Based on the investigation,the following recognitions are obtained by segmental analysis: Seismic geological disasters occur mainly at thin ridges and steep slopes,rockfalls occur mostly at rock slopes,and landslides occur at loose deposited slopes,but large-scale landslides are rare.The overall revival of large-scale loose deposits is not caused by the earthquake,and only some collapse or vibration cracks take place in some parts of steep-gentle junctions.Thus,the loose deposited ancient landslides are stable.This suggests that strong earthquake may not induce overall revival of ancient landslides.
Even though Lushan 4·20 strong earthquake has characteristics of high seismic magnitude and strong destructiveness,its secondary geological disasters are dominated by rockfalls rather than landslides.Compared with secondary geological disasters induced by 5·12 Wenchuan earthquake,their size and number are both mild.However,Baoxing County,which is in the earthquake-affected zone,is an exception.Rockfalls and landslides develop well around the county because of steep mountains.Geological field investigations of the geohazards around Baoxing County before and after the earthquake show that after earthquake the number of rockfall,landslide and debris flood changes into 21,1,and 3 from 3,1,and 3,respectively;geohazards development density and modulus change into 2.02 km-1 and 5.59×104 m3/km from 0.38 km-1 and 3.4×103 m3/km,respectively,which are 5.3 and 16.4 times that before the earthquake;and the effect of slope failure induced by the earthquake is significant.Based on the investigation,the following recognitions are obtained by segmental analysis: Seismic geological disasters occur mainly at thin ridges and steep slopes,rockfalls occur mostly at rock slopes,and landslides occur at loose deposited slopes,but large-scale landslides are rare.The overall revival of large-scale loose deposits is not caused by the earthquake,and only some collapse or vibration cracks take place in some parts of steep-gentle junctions.Thus,the loose deposited ancient landslides are stable.This suggests that strong earthquake may not induce overall revival of ancient landslides.
引文
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[10]黄润秋.汶川8.0级地震触发崩滑灾害机制及其地质力学模式[J].岩石力学与工程学报,2009,28(6):1239-1249.HUANG Runqiu.Mechanism and geomechanicalmodes of landslide hazards triggered by Wenchuan 8.0earthquake[J].Chinese Journal of Rock Mechanicsand Engineering,2009,28(6):1239-1249.
[11]XU Wenjie,XU Qiang,WANG Yujie.Themechanism of high-speed motion and damming of theTangjiashan landslide[J].Engineering Geology,2013,157:8-20.
[12]YIN Yueping,WANG Fawu,SUN Ping.Landslidehazards triggered by the 2008 Wenchuan earthquake,Sichuan,China[J].Landslides,2009,6(2):139-151.
[13]钱江鹏.4.20芦山地震震后宝兴县城周围地质灾害危险性评估报告(生产报告)[R].成都:四川省地质工程勘察院,2013.
[2]黄润秋,李为乐.5.12汶川大地震触发地质灾害的发育分布规律研究[J].岩石力学与工程学报,2008,27(12):2585-2592.HUANG Runqiu,LI Weile.Research on developmentand distribution rules of geohazards induced byWenchuan earthquake on 12th May,2008[J].ChineseJournal of Rock Mechanics and Engineering,2008,27(12):2585-2592.
[3]黄润秋.“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.HUANG Runqiu.Characteristics of geological disastersof 5.12 Wenchuan earthquake and recommendation onits impact on reconstruction[J].Chinese GeologicalEducation,2008(2):21-24.
[4]黄润秋,许强.中国典型灾难性滑坡[M].北京:科学出版社,2008:525-553.
[5]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(3):433-454.HUANG Runqiu.Large-scale landslides and theirsliding mechanisms in China since the 20th century[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(3):433-454.
[6]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 on 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.
[7]胡卸文,朱海勇,吕小平,等.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[J].四川大学学报:工程科学版,2009,41(3):63-71.HU Xiewen,ZHU Haiyong,LXiaoping,et al.Research on trigger effecting of earthquake geohazards intangjiashan dammed lake(Beichuan to Yuli)[J].Journal of Sichuan University:Engineering ScienceEdition,2009,41(3):63-71.
[8]顾成壮,胡卸文,罗刚,等.地震滑坡启程动力学机理[J].西南交通大学学报,2012,47(4):567-572.GU Chengzhuang,HU Xiewen,LUO Gang,et al.Setting-out mechanism of landslide induced byearthquake[J].Journal of Southwest JiaotongUniversity,2012,47(4):567-572.
[9]张鹏,陈新民,王旭东.近断层地震动与汶川地震灾区滑坡破坏特征分析[J].南京工业大学学报:自然科学版,2009,31(1):55-59.ZHANG Peng,CHEN Xinmin,WANG Xudong.Analysis of near-fault ground motion and seismiclandslide failure mode in Wenchuan earthquake[J].Journal of Nanjing University of Technology:NaturalScience Edition,2009,31(1):55-59.
[10]黄润秋.汶川8.0级地震触发崩滑灾害机制及其地质力学模式[J].岩石力学与工程学报,2009,28(6):1239-1249.HUANG Runqiu.Mechanism and geomechanicalmodes of landslide hazards triggered by Wenchuan 8.0earthquake[J].Chinese Journal of Rock Mechanicsand Engineering,2009,28(6):1239-1249.
[11]XU Wenjie,XU Qiang,WANG Yujie.Themechanism of high-speed motion and damming of theTangjiashan landslide[J].Engineering Geology,2013,157:8-20.
[12]YIN Yueping,WANG Fawu,SUN Ping.Landslidehazards triggered by the 2008 Wenchuan earthquake,Sichuan,China[J].Landslides,2009,6(2):139-151.
[13]钱江鹏.4.20芦山地震震后宝兴县城周围地质灾害危险性评估报告(生产报告)[R].成都:四川省地质工程勘察院,2013.
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