Abstract: In the stability analysis of earthquakeinduced slope instability, in order to demonstrate the dynamic failure mode of slopes, quantitative indicators of the permanent displacement are often used. The influence of vertical ground motion on slope stability has always been a controversial issue when studying the permanent displacement of slopes. Based on the classical Newmark method, this paper uses the vertical seismic coefficient λ to indicate the degree of vertical seismic inertial force, the classic three major seismic waveforms measured by the input station, and compare the effects of different degrees of vertical acceleration on the slope stability. It shows that the existence of vertical acceleration is particularly significant for the slope. Considering the vertical acceleration coefficient λ is positive, it will have a significant impact on the stability of the slope, and the highest can be achieved without considering the permanent displacement of the vertical acceleration. When comparing the effects of different angles on slope stability, it is found that slopes with slower slopes are prone to greater displacement growth rates. Many times, so in the design of seismic slopes, the influence of vertical acceleration on the slope cannot be ignored.

Key words: Permanent Displacement, Vertical Ground Motion, Newmark Method, Vertical Acceleration Coefficient