Guantan landslide is a typical anti-dipped rock slope with soft foundation, a result of combined action of Wenchuan earthquake and rainfall after the earthquake. This paper built numerical analysis models of a slope with or without soft foundation. It revealed influence induced by soft foundation to evolution of stress field and extending trend of rupturing process of the slope during earthquake dynamic response process. Calculated result shows that before the failure of the slope, the existence of soft foundation can reduce the role of earthquake dynamic effect to a certain extent,which is positive to slope stability. But once the slope failed,the existence of soft foundation may intensify extension and coalescence of rupture surface,and finally form landslide.%罐滩滑坡是“5·12”地震诱发的典型反倾软弱基座滑坡,滑坡在地震过程中并末立即滑移,而是在震后余震和降雨共同作用下产生的.为研究滑坡中下部软基在地震过程中对滑坡稳定性的影响,本文以罐滩滑坡的地质结构为背景,建立了有无软弱基座2种结构斜坡的概化模型,通过数值计算揭示了斜坡在地震动力响应过程中的应力演化过程及其破裂的产生和延展趋势.计算结果表明:在斜坡发生破坏之前,软弱基座的存在一定程度上起隔震作用,对斜坡的稳定有利；一旦斜坡整体性遭到破坏,软弱基座的存在会加剧破裂面的延伸和贯通,最终导致形成滑坡.
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