Discrete element simulation of the Jiufengershan rock‐and‐soil avalanche triggered by the 1999 Chi‐Chi earthquake, Taiwan

Abstract

[1] We present Contact Dynamics discrete element simulations of the earthquaketriggered Jiufengershan avalanche, which mobilized a 60 m thick, 1.5 km long sedimentary layer, dipping $22°SE toward a valley. The dynamic behavior of the avalanche is simulated under different assumptions about rock behavior, water table height, and boundary shear strength. Additionally, seismic shaking is introduced using strong motion records from nearby stations. We assume that seismic shaking generates shearing and frictional heating along the surface of rupture, which, in turn, may induce dynamic weakening and avalanche triggering; a simple ''slip-weakening'' criterion was adopted to simulate shear strength drop along the rupture surface. We investigate the mechanical processes occurring during triggering and propagation of an avalanche mobilizing shallowly dipping layers. Incipient deformation forms a pop-up structure at the toe of the dip slope. As the avalanche propagates, the pop-up deforms into an overturned fold, which overrides the surface of separation along a décollement. Simultaneously, uphill layers slide at high velocity (125 km/h) and are folded and disrupted as they reach the toe of the dip slope. The avalanche foot forms a wedge that is pushed forward as deformed rocks accrete at its rear. We simulated five cross sections across the Jiufengershan avalanche, which differ in the geometry of the surface of separation. Topographic and simulated surface profiles are similar. The friction coefficient at the surface of separation determined from back analysis is abnormally low (m SS = 0.2), possibly due to lubrication by liquefied soils. The granular deposits of simulated earthquake-and rain-triggered avalanches are similar.

On the Dynamic Fragmentation and Lubrication of Coseismic Landslides

“…The intensity of particle agitation can be quantified by the vibrational and rotational granular temperatures in Figure 11a. In addition, the fracturing and fragmentation of rock also involve intense energy dissipations, together with boosts of granular momentum for some rock fragments, leading to the increase of landslide mobility ( According to Campbell et al (1995), Strom (1999), and Chang and Taboada (2009), even though intense shearing exists within a completely fragmented slope, the landslide debris deposit exhibits approximately the same strata order as its original stratigraphic structure in the source mountainside after a long runout. This feature can also be well illustrated in the current study on the dynamic fragmentation of an initially intact rock slope ( Figure 5).…”

Ensemble Empirical Mode Decomposition With Supervised Cluster Analysis

“…On the 21th September 1999, the Chi-Chi earthquake in Taiwan triggered a major landslide in the Tsaoling area [Hung (2000); Chang and Taboada (2009)]. The detached landslide mass had a volume about 125 × 10 6 m 3 .…”

Exploring the Evolution of Lateral Earth Pressure using the Distinct Element Method

“…However, many researchers have reported that the behavior of geo-materials can still be adequately captured by DEM despite these simplifications (Calvetti and Emeriault, [11]; Potyondy and Cundall, [12]; Cui and O'Sullivan, [13]; Cho et al, [14]; Wang and Leung, [15]; Hsieh et al, [16], Schopfer et al [17]). In addition, the DEM has been successfully applied to many areas of engineering, such as soil mechanics, rock engineering, tunneling, and landslide evaluation (Hentz et al, [18]; Utili and Nova, [19]; Sitharam et al, [20]; Chang and Taboada, [21]). …”