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Abstract Collapsing and sliding responses of Tangjiashan landslide near Beichuan county and its running out process triggered by time difference coupling effects(considering horizontal and vertical seismic force effects all together)，the regionality and spatial heterogeneity of P and S seismic waves generating horizontal and vertical seismic loads are elaborated；and formation mechanism and key controlling factors of collapsing and sliding of the slope are confirmed by applying DEM numerical simulation. The result shows that initial collapsing and sliding of the slope are triggered by combined action of horizontal and vertical tension caused by P seismic wave，and the vertical tension plays a superiority role. Ejecting and flowing of the broken slope mass are triggered by combined action of P and S seismic waves. Secondly，combined action between horizontal and vertical tension of P wave is the key controlling factor inducing the slope collapsing and sliding. At the same time，slope topography is the key controlling factor leading to collision and debris flow of the slope mass fractured in latter process. Finally，amplification effect of parameters in slope dynamic response shows that the amplification coefficient of vertical acceleration is larger than that of horizontal acceleration，and the vertical velocity and horizontal velocity decreasing one by one，and this trend is consistent with key controlling factor inducing slope fracturing，i.e. vertical seismic loads playing a superiority role. It is of great theoretical and practical value for studying collapsing and sliding of slopes triggered by seismic loads.
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Received: 27 July 2009
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