Dynamic disintegration processes accompanying transport of an earthquake-induced landslide
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Ge Gao I Mohamed A. Meguid I Luc E. Chouinard I Weiwei Zhan
Dynamic disintegration processes accompanying transport of an earthquake-induced landslide
Abstract Aiming to understand the dynamic disintegration and transport behavior of an earthquake-induced landslide, a dynamic discrete element method has been employed to analyze the Wangjiayan landslide triggered by the 2008 Ms 8.0 Wenchuan earthquake. Absorbing boundary condition is used for the seismic wave transmission and reflection at the slope base. The numerical results show that under seismic loading, internal rock damage initiates, propagates, and coalesces progressively along the weak solid structure and subsequently leads to fragmentation and pulverization of the slope mass. This can be quantitatively interpreted with the continuously rapid increase of the damage ratio and sudden decline of growth ratio of the number of fragments after the peak seismic shaking. During emplacement evolution, fragmented deformation patterns within the translating jointdefined granular assemblies are affected by the locally high dilatancy with a simultaneous occurrence of highly energetic collisions related to the action of shearing, and this can be quantified by the enhancement of particle kinematic activities (high vibrational and rotational granular temperatures) and intense fluctuations of location-dependent global dispersive stress. In this process, slope destabilized and transports downward in a rapid pulsing motion as friction bonds are locally and continually overcome by the seismic- and gravity-induced shear forces. The joint-determined fragment network before movement initiation and the final fragmented depositions after the rapidly sheared transport have been systematically investigated by fragment statistics (fragment size distribution, fragment mass distribution, and fractal dimension) and morphometric characters (fragment shape isotropy) to offer new insights into the disintegration characteristics of the earthquake-induced catastrophic mass movements. Keywords Earthquake-induced landslide . Discrete element method . Absorbing boundary condition . Dilatancy . Fragmentation Introduction Earthquake-induced landslides are among the natural hazards that can pose serious threats to communities and infrastructures. Many catastrophic landslides of this type have recently occurred worldwide, in particular, the 2008 Mw 7.9 Wenchuan earthquake has triggered more than 56,000 landslides in steep mountainous terrain covering an area of about 41,750 km2 (Wang et al. 2009; Dai et al. 2011). The landslides directly caused more than 20,000 fatalities (Yin et al. 2009). In light of the catastrophic instability and disastrous consequence, there has been an increasing interest in the study of earthquake-triggered landslides; however, much uncertainty still exists about co-seismic slope fragmentation and emplacement mechanism. The landslide is always associated with rock fragmentation together with high spreading velocities, long runouts, and energy release; however, the process o
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