地震动力作用触发的斜坡崩滑效应模拟

Numerical Simulation of Collapsing and Sliding Response of Slope Triggered by Seismic Dynamic Action

摘要:

依据震后实地调查中竖向地震力作用十分明显的现象,突破传统斜坡动力反应分析中仅考虑水平地震力作用的局限,运用离散元数值模拟技术,对北川王家岩斜坡体在具地域性和空间非均质性的地震纵横波时差耦合作用下产生崩滑破坏的动力全过程进行了模拟,确定了地震动力作用下该斜坡体崩滑破坏的形成机制及主控因素.研究表明:该斜坡体的初期崩滑破坏是受到纵波产生的水平和竖向拉裂耦合作用所致,且以水平拉裂作用占优,而后期的抛射及碎屑流动则是受到纵横波耦合作用所致;即纵波的个体作用是触发斜坡体产生初期崩滑破坏的主控因素,而斜坡体所处地形则是促使破坏后的斜坡体形成后续碰撞解体及碎屑流动的主控因素.

Abstract:

A simulation was carried out on initial collapsing-sliding and a subsequent running out process of Wangjiayan Landslide in Beichuan County during the Wenchuan Earthquake triggered by single and combined action with time difference, regionality and spatial heterogeneity of primary and secondary seismic waves based on discrete element method by taking into the consideration the fact that vertical ground motion was still evident in post-earthquake field geological investigation, and formation mechanism and key controlling factors of slope collapsing and sliding under seismic load were determined,which was different with the traditional dynamic response analysis based on a consideration of horizontal seismic load. The result shows that initial collapsing and sliding of the slope are triggered by combined action of vertical and horizontal tension, which plays a dominant role,of primary seismic wave, whereas a subsequent collision and debris flow of slope mass fractured are triggered by combined action of primary and secondary seismic wave. On the other hand, single action of primary seismic wave is the key controlling factor inducing the slope initial collapsing and sliding, and the topography near the slope is the key controlling factor leading to collision and debris flow of the slope mass fractured in later process.