Abstract
Abstract. The huge Donghekou landslide was triggered by the Wenchuan earthquake in 2008 with about 2.4 × 107 m3 of rock displaced. The landslide is considered as an example of an earthquake-induced "ejection" event, where dislocated slope materials was expelled over a section of the slope, but the kinematic processes are not well understood. We used the 2-D granular discrete element method to characterize the kinematic behavior and mechanics of this "ejection landslide". The initial boundary conditions were applied along the ball–wall contacts by using derived velocities integrated from strong motion data with a duration of 125 s, including the peak acceleration near the Donghekou area. The constraints were primarily determined from the final geometry of the landslide and geological structures to account for the actual landslide characteristics. Simulated results showed that the large local seismic acceleration and a free face under the sliding body, caused by the dip difference between the upper slide face and the natural slope, originated from the activation of the landslide. For the lower sliding body, its kinematic mechanism was changed during sliding. Initially it was a push-type landslide, and then gradually changed to a retrogressive landslide. The eroded bed on the slope during the landslide had the potential of slightly increasing the runout distance from 1435 to 1519 m, and was predicted in the numerical simulation.
Highlights
Earthquakes cause large-scale ground movement and can trigger severe landslides over broad areas resulting in serious damage and casualties (Harp and Jibson., 1996; Central Geological Survey, 2000; Chigira et al, 2003; Keefer et al, 2006; Keefer and Larsen, 2007; Dai et al, 2010)
This research validated numerical modeling based on discrete element methods, which is a powerful tool for modeling rock slope failure due to seismic shaking
Yuan et al.: Mechanism of the Donghekou landslide technique is commonly used for modeling granular assemblages with purely frictional or bonded circular particles represented by discs and is widely used to resolve rock engineering and geomechanics problems (e.g., Wang et al, 2003; Potyondy and Cundall, 2004; Tang et al, 2009a, b, 2013, 2014)
Summary
Earthquakes cause large-scale ground movement (shaking) and can trigger severe landslides over broad areas resulting in serious damage and casualties (Harp and Jibson., 1996; Central Geological Survey, 2000; Chigira et al, 2003; Keefer et al, 2006; Keefer and Larsen, 2007; Dai et al, 2010). The complex kinematics of the flowing mass depends on the morphological and geological characteristics of the slope, rheology of the surface material, and the triggering process. Yuan et al.: Mechanism of the Donghekou landslide many researchers have adopted discrete element methods to analyze landslides (Campbell et al, 1995; Poisel and Roth 2004; Poisel et al, 2005; Staron, 2007; Peng, 2008; Tang et al, 2009a, b, 2013). This research validated numerical modeling based on discrete element methods, which is a powerful tool for modeling rock slope failure due to seismic shaking. We try to address some special phenomena of the Donghekou landslide using the 2-D discrete element method for granular materials, which is helpful for characterizing the complex kinematics and triggering process of a large landslide. We focus especially on explaining the ejection of the upper landslide body and the formation of two disconnected landslide surfaces
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