金鼓高速远程滑坡形成机制及动力稳定性

FORMATION MECHANISM AND DYNAMIC STABILITY OF JINGU HIGH-SPEED AND LONG-RUN-OUT LANDSLIDE

综合运用多学科理论和方法,对汶川地震触发的金鼓高速远程滑坡形成机制及动力稳定性进行研究。在工程地质定性研究方面,通过对滑坡区的地形地貌、地层岩性、构造与地震以及水文地质条件的综合研究,分析高速远程滑坡的形成机制,将其划分为紧密发生的2个演化阶段:第一阶段为上部滑体被抛掷分离,第二阶段为下部受铲刮发生二次滑坡。在岩土力学定量研究方面,进行以下3个方面的工作:(1)以FLAC3D作为动力分析的数值计算引擎,采用自行开发的基于多层次微粒群的非圆弧最危险滑动面搜索并行程序,获得滑坡的动力稳定系数时程及其对应的最危险滑动面的空间分布规律,研究动力稳定系数的频域特征;(2)通过2种潜在破坏模式的对比研究,指出金鼓高速远程滑坡2#滑动面簇发生主导破坏的可能性更大,并可触发二次滑坡;(3)依据空气动力学定量计算,论述上部滑体长距离抛掷是完全有可能的。综合研究表明,岩土力学定量分析结果与工程地质定性成果相吻合,进而将金鼓高速远程滑坡孕育的先决条件归纳为以下4条:力学性质差、高位剪出、下降空间开阔、初速度足够大。

Based on integrating the theories and methods of multi-discipline,the research on formation mechanism and dynamic stability of Jingu landslide,a high-speed and long-run-out landslide induced by Wenchuan earthquake,was conducted.In the aspect of qualitative study of engineering geology,the formation mechanism of Jingu landslide was analyzed after comprehensive investigation involved in topography,lithology,tectonics and earthquake,as well as hydrogeology.As a result,the evolutionary stage of Jingu landslide was divided into two closely-linked phases.First,the upper sliding body was separated and thrown across the river standing at the toe of landslide.Second,the lower part of the slope was developed into a secondary landslide by the scratch from the upper body.On the other aspect of rock and soil mechanics quantitative study,three tasks were performed as follows：（1） Based on the fast Lagrangian analysis of continua in 3 dimensions（FLAC3D） dynamic analysis and a multilayer particle swarm optimization technique,a self-made parallel searching program was utilized to locate the non-circular critical slip surfaces of the landslide and its corresponding time-histories of dynamic factor of safety,of which frequency characteristics were revealed by spectrum analysis.（2） Based on the comparative study of two potential failure modes,the cluster #2 of slide surfaces is more possible to dominate the whole failure and trig the secondary landslide of slope.s lower part.（3） By aerodynamics calculation,long-distance throwing of upper sliding body is entirely possible.Comprehensive studies have shown that the quantitative analysis results of rock and soil mechanics are consistent with the engineering geology qualitative analysis results.The four prerequisites of the development of Jingu landslide were summarized as follows：poor mechanical properties,high position of shear crack,open terrain in lowering direction and enough initial velocity.