强震触发崩塌滚石运动特征研究
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摘要
高强度、长持时汶川地震诱发大量边坡滚石,滚石源于岩体结构面切割而成的块体或岩土质边坡中尺寸较大的孤石。以汶川地震未扰动现场滚石痕迹的判识、测量取样及分析,得出强震作用下块体(石)是以一定初始速度抛射而出的;其坡面运动表现为滑动、滚动、跳跃与3种方式的组合。选取2个典型强震崩塌点为例进行研究,基本结论:(1)与重力作用下崩塌滚石运动特征是有显著区别的,地震触发滚石具有一定的平抛速度,初始速度除与地震烈度有关外,还与地形地貌有关,其中变坡点、凸起点、端部速度较大;(2)滚石三边(长、宽、高)比例越接近,其运距越远;坡面相对1/2高度以上,运动方式表现为跳跃-滚动、跳跃-滑动为主,其下滚石则以滑动、滚动运动为主;(3)规模(质量)大的滚石多停留于第一着地点附近或边坡坡脚宽缓地带,滚石运动消能方式为摩擦或碰撞解体;滚石平台阻滞率为54%,树(灌)木拦阻率为12%。通过反演,计算了非弹性碰撞法向恢复系数Rn与切向恢复系数Rt,其中裸露基岩Rn=0.2,Rt=0.6,一般覆盖层Rn=0.3,Rt=0.8。滚石在运动过程中的弹跳理论高度在0.2～1.3m之间,坡面相对高差与最远滚动距离之比约为1/2。
Wenchuan Earthquake,with high intensity and long period,caused masses of rolling rocks which derived from block stones of rock slopes divided by structure faces and big size corestones of soil slope.The block stones are projected with initial speeds.Their movements on slope surfaces are the combination of sliding,rolling and jumping.Based on the field investigation,this paper chooses two typical unsteady slopes caused by the earthquake to study movement characters of rolling rocks.Three findings are as follows.(1)The more the rolling rocks have equal three dimensions in length,width,and height,the farther the rock movement distance.But for platy rolling rocks,if their narrow side touchdown firstly,and collide elasticcally,they will jump at a high speed and move long-distance;(2)At the 1/2 height of slope surface or higher,rolling rock movement is sliding,rolling mainly.At the lower positions,it is jumping-rolling,jumping-sliding;(3)Big size(mass)rolling rocks mostly stay at the first touchdown or the wide gently areas at the slope toe areas.The way to consume energy is friction or collision disintegration,in which the ratio of platform block is 54% and trees(shrub) is 12%.By inversion,renew coefficient Rn and Tangentially renew coefficient Rt are obtained.For the bare bedrocks,Rn=0.3 and Rt=0.6.For the overlay,Rn=0.2and Rt=0.8.For moving rolling rocks,their bounce heights are between 0.49～3.10m.The ratio of the maximum rolling height and the farthest movement distance is 1/2.
Wenchuan Earthquake,with high intensity and long period,caused masses of rolling rocks which derived from block stones of rock slopes divided by structure faces and big size corestones of soil slope.The block stones are projected with initial speeds.Their movements on slope surfaces are the combination of sliding,rolling and jumping.Based on the field investigation,this paper chooses two typical unsteady slopes caused by the earthquake to study movement characters of rolling rocks.Three findings are as follows.(1)The more the rolling rocks have equal three dimensions in length,width,and height,the farther the rock movement distance.But for platy rolling rocks,if their narrow side touchdown firstly,and collide elasticcally,they will jump at a high speed and move long-distance;(2)At the 1/2 height of slope surface or higher,rolling rock movement is sliding,rolling mainly.At the lower positions,it is jumping-rolling,jumping-sliding;(3)Big size(mass)rolling rocks mostly stay at the first touchdown or the wide gently areas at the slope toe areas.The way to consume energy is friction or collision disintegration,in which the ratio of platform block is 54% and trees(shrub) is 12%.By inversion,renew coefficient Rn and Tangentially renew coefficient Rt are obtained.For the bare bedrocks,Rn=0.3 and Rt=0.6.For the overlay,Rn=0.2and Rt=0.8.For moving rolling rocks,their bounce heights are between 0.49～3.10m.The ratio of the maximum rolling height and the farthest movement distance is 1/2.
引文
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[7]黄达,黄润秋,周江平,裴向军,刘卫华.雅砻江锦屏一级水电站坝区右岸高位边坡危岩体稳定性研究[J].岩石力学与工程学报,2007,26(1):175～181.Huang Da,Huang Runqiu,Zhou Jiangping,Pei Xiangjun,LiuWeihua.Study on stability evaluation of unstable rock masses onright bank high altitude slope in the first stage Jinping hydropowerstation.Chinese Journal of Rock Mechanics and Engineering,2007,26(1):175～181.
[8]Shang YJ,Wang S J,Li G C,et al.Retrospective case example u-sing a comprehensive suitability index(CSI)for siting the Shisan-ling power station,China[J].International Journal of Rock Me-chanics and Mining Sciences,2000,37(5):839～853.
[9]黄润秋,刘卫华,周江平等.滚石运动特征试验研究[J].岩土工程学报,2007,29(9):1296～1302.Huang Runqiu,Liu Weihua,Zhou Jiangping.Rolling tests onmovement characteristics of rock blocks.Chinese Journal ofGeotechnical Engineering,2007,29(9):1296～1302.
[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,2009,16(1):29～38.Yin Yaoping.Features of landsl ides triggered by the Wenchuanearthquake,2009,16(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,Xu Qide,Xu Bin,Zhang Wei.Emergency remotesensing survey of“5.12”Wenchuan strong earthquake.ScienceIn China,Technological Sciences(E),2009,39(7):1304～1311.
[4]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,2009,6:1239～1249.Huang Runqiu.Mechanism and geomechanical modes of landslide-hazards triggered by Wenchuan 8.0 earthquake,2009,6:1239～1249.
[5]叶四桥,陈洪凯,唐红梅.重庆市万州区太白岩危岩综合治理[J].重庆交通学院学报,2004,23(1):85～89.Ye Siqiao,Chen Hongkai,Tang Hongmei.Synthetic treatment ofTaibaiyan dangerous rock in Wanzhou district of Chongqing.Journal of Chongqing Jiaotong University,2004,23(1):85～89.
[6]陈洪凯,唐红梅,刘光华,等.危岩支撑及支撑-锚固联合计算方法研究[J].岩土工程学报,2004,26(3):383～388.Chen Hongkai,Tang Hongmei,Liu Guanghua,et al.Research oncalculation method of support and support anchorage union to un-stable rock.Chinese Journal of Geotechnical Engineering,2004,26(3):383～388.
[7]黄达,黄润秋,周江平,裴向军,刘卫华.雅砻江锦屏一级水电站坝区右岸高位边坡危岩体稳定性研究[J].岩石力学与工程学报,2007,26(1):175～181.Huang Da,Huang Runqiu,Zhou Jiangping,Pei Xiangjun,LiuWeihua.Study on stability evaluation of unstable rock masses onright bank high altitude slope in the first stage Jinping hydropowerstation.Chinese Journal of Rock Mechanics and Engineering,2007,26(1):175～181.
[8]Shang YJ,Wang S J,Li G C,et al.Retrospective case example u-sing a comprehensive suitability index(CSI)for siting the Shisan-ling power station,China[J].International Journal of Rock Me-chanics and Mining Sciences,2000,37(5):839～853.
[9]黄润秋,刘卫华,周江平等.滚石运动特征试验研究[J].岩土工程学报,2007,29(9):1296～1302.Huang Runqiu,Liu Weihua,Zhou Jiangping.Rolling tests onmovement characteristics of rock blocks.Chinese Journal ofGeotechnical Engineering,2007,29(9):1296～1302.
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