皂角沱崩塌形成机制数值模拟

Numerical Simulation of Formation Mechanism of the Zaojiaotuo Collapse

以位于"5·12"汶川大地震震中区的皂角沱崩塌为研究对象,通过对崩塌所处的自然地理、工程地质环境进行野外调查,分析崩塌的发育特征;采用不连续变形分析软件DDA,对坡体失稳崩塌的全过程进行模拟研究。结果表明,斜坡地形放大效应在震中区是客观存在的,具倾向坡外的陡倾控制性结构面的高陡突出地形对地震波具有明显的放大作用。该坡体崩塌失稳模式为:峰值加速度放大→增加的振幅迫使岩体沿陡倾坡外的控制性结构面迅速拉裂→沿滑动面发生崩滑→高速脱离滑源区→巨大的势能和动能驱动块体做长距离运动。通过数值模拟可知,随着斜坡坡高的增大,地震加速度和速度无论是在水平向,还是在竖直向均存在放大效应,但是水平向的放大效应较竖直向更明显;结构面监测点的加速度和速度放大系数相比稳定的坡体要大得多,地震袭来,当遇到陡倾坡外的不连续结构面时,斜坡动力响应强烈,最终危岩体沿控制性结构面发生崩滑破坏。

＂ 5. 12＂ Wenchuan earthquake induced extensive collapse disasters in the epicentral area,which has caused huge losses to the local people＇s lives and property. In this paper,we choose the Zaojiaotuo collapse in the epicentral area as research object,based on detailed field investigation of the collapse＇s natural geography and engineering geological environment,analyses and judge the development characteristics of the collapse masses. Using the Discontinuous Deformation Analysis software,DDA,to simulate the whole process of the landslide. The results show that,slope topography amplification effect in the epicentral area performs significantly,a high and steep terrain with an inclined bedding slope controlled by steep structure plane,has a significant amplified effect on seismic wave. Amplify peak acceleration→the increasing amplitude forces rock mass along the controlling structure planes which parallel with slope to crack quickly→rock masses collapse along the slip surface→high-speed detach from the slipping source region→huge potential and kinetic energy drive rock mass to do long-distance movement. The numerical simulation analysis shows that,with the increase of slope height,particles＇ acceleration and velocity in the slope body has significant terrain amplification effects under the action of seismic force. However,the horizontal magnification effect is more obvious than the one of the vertical direction. The amplification factor of monitoring point＇s acceleration and velocity in structure plane is much greater than that in the stable slope,when seismic waves face with discontinuously steep structural surfaces which incline to the slope outside,the dynamic response of slope becomes strong and eventually lead to slope＇s instability.