考虑动态临界加速度的地震边坡永久位移研究

Newmark永久位移是评价边坡在地震时稳定性的一个重要指标,近年来广泛应用于地震边坡危险性评价中。传统Newmark永久位移法在计算临界加速度时假定其为常数,未考虑滑动面上抗剪强度参数的变化,过低估计了边坡的永久位移。为了解决这一问题,本文从岩土结构理论获得思路,详细分析滑块底面抗剪强度参数在地震中的变化过程,以边坡震动过程中黏聚力逐步丧失为基本思路,在黏聚力符合一定概率分布的基础上,提出了一种利用蒙特卡罗法模拟其动态减小过程从而实现临界加速度动态变化的计算方法。经过算例计算,黏聚力和临界加速度体现了地震过程中边坡滑块黏聚力和临界加速度的动态变化,位移大小符合地震边坡实际位移的常规数值。本文提出的蒙特卡罗法实现动态黏聚力和动态临界加速度的计算过程与地震时程相对应,不仅在一定程度上解决了抗剪强度参数的动态变化问题,还解决了传统Newmark位移计算中永久位移比实际位移偏小的问题。

Study of Seismic Slope Permanent Displacements with Dynamic Critical Acceleration

The Newmark permanent displacement, an important index for evaluating the stability of slopes in earthquakes, is extensively applied to seismic slope hazard assessment. However, because the critical acceleration is assumed to be constant and the variations of shear strength parameters on sliding surfaces are not considered in the traditional Newmark permanent displacement method, the permanent displacements of a slope are often underestimated. To solve this problem, this paper analyzes the change process of shear strength parameters on a sliding surface in detail based on geotechnical structure theory. A method to calculate the dynamic critical acceleration in which the dynamic change of cohesion is simulated by the Monte Carlo method on the basis of a certain probability distribution type of cohesion is presented. Sample calculations reveal the dynamic change processes of cohesion and critical acceleration of the slope sliding block in earthquake, and a new permanent displacement result is obtained. The displacement results conform to the normal displacement value of the seismic slope, and the implementation processes of dynamic cohesion and critical acceleration presented in this paper correspond to the seismic time history. Dynamic changes in shear strength parameters are solved to a certain extent, and the displacement problem encountered in the traditional Newmark permanent displacement calculation is addressed.