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.
出处
《工程地质学报》
CSCD
北大核心
2011年第4期498-504,共7页
Journal of Engineering Geology
基金
国家自然科学基金(40972195)
地质灾害防治与地质环境保护国家重点实验室自由探索基金(SKLGP2009Z009)
教育部创新团队计划基金(IRT0812)
关键词
汶川地震
边坡滚石
运动特征
消能方式
恢复系数
Wenchuan earthquake
Slope rolling rock
Movement character
Consume energy
Renew coefficient
