强度折减中滑坡启动阶段的动力分配原理

Mechanism of dynamic distribution in the stage of landslide initiation with shear strength reduction

对于推移式滑坡,传统的稳定性分析运用静力平衡条件求解滑坡稳定系数。剩余推力法将滑面简化为折线,利用垂直条分法进行极限稳定分析,其广泛应用于我国建筑、水利、铁路、公路等各行业。基于剩余推力法的基本假定,通过抗剪强度折减使滑坡逐渐失稳,假定各条块水平加速度相同并根据牛顿第二定律建立一组滑坡动力平衡方程,利用动力分配系数对下滑动力进行分配,折减过程反映了滑坡由极限稳定到失稳时的条块动力分配过程,首次实现滑坡动力平衡和静力平衡的统一表达,建立动力分配法。该方法继承了潘家铮法的基本假定并拓展了Sarma法,计算的滑坡稳定系数与剩余推力法的计算结果完全吻合,计算的滑坡加速度与潘家铮法相近并提高了准确性,得到了折减系数的倒数与滑坡加速度为线性关系的重要推论,由此阐述了滑坡位移的力学机制。动力分配法兼顾了滑坡的动力平衡与静力平衡,物理意义明确,计算结果正确,奠定了滑坡启动阶段的动力学基础,具有深刻的理论意义和广泛的工程意义。

The stability coefficient of slopes is derived generally according to the static equilibrium equations. The sliding surface is simplified to be a line chain and the slope is sliced vertically in the method of residual thrust. This paper presents a method to calculate the stability coefficient by means of shear strength reduction. A set of equilibrium equations for sliced slopes was established on the assumption of invariable horizontal acceleration within the sliding blocks. The sliding force of the slope was controlled by the dynamic distribution coefficient. The dynamic distribution process of sliding mass from stable to instable was described usually by the process of shear strength reduction. The unified expression between the dynamic and static equilibrium of the slope was derived firstly in this article. The dynamic distribution principle has not only inherited Panjiazheng principle but also developed Sarma method. The computed stability coefficient was identical to that of residual thrust principle,and the computed acceleration was similar to but more accurate than that from Panjiazheng principle. An important conclusion of this article is that the reduction coefficient was linear to the sliding acceleration of slope,which played a critical role in explaining the dynamic mechanism of landslide displacement.