Abstract:

Near-fault pulse-like ground motions are characterized by long periods, large amplitudes, and high energy release, exhibiting significantly higher destructive power than conventional ground motions. However, the dynamic response characteristics and failure mechanisms of slopes subjected to pulse-like ground motions remain unclear. Based on the universal distinct element code (UDEC), a generalized model of opposing rock slopes in a valley was established, and the dynamic response characteristics of rock slopes under pulse-like ground motions were systematically analyzed. Additionally, the relationship between the directional asymmetry in pulse-like ground motion intensity and the aspect effects of earthquake-induced landslides was investigated. The results indicate that, under typical pulse-like ground motions, the dynamic response of the opposing rock slopes in the valley is strongest during the velocity pulse phase. The maximum acceleration amplification factor on the right slope reaches 1.57 times that of the left slope, with the cumulative displacement being as much as twice that of the left slope. Pulse-like ground motions generally exhibit pronounced directional asymmetry in intensity, which is a key dynamic mechanism leading to significant aspect effects of earthquake-induced landslides. The amplitude-based index, peak ground velocity (PGV), demonstrates the highest correlation coefficient (r=0.82) with cumulative slope displacement, significantly surpassing other indexes such as peak ground acceleration (PGA), Arias intensity (Ia), specific energy density (SED), velocity-to-acceleration ratio (V/A). It is the most accurate ground motion intensity index for characterizing the directional intensity differences of pulse-like ground motions and their impacts on the stability of slopes with different orientations. The research outcomes offer scientific underpinning for analyzing slope stability and assessing seismic landslide hazards under the influence of pulse-like ground motions.

Key words: pulse-like ground motions, UDEC, dynamic response, aspect effect, ground motion intensity measures