ORIGINAL RESEARCH published: 02 August 2021 doi: 10.3389/feart.2021.710031 Dynamic Process and Mechanism of the Catastrophic Taihongcun Landslide Triggered by the 2008 Wenchuan Earthquake Based on Field Investigations and Discrete Element Method Simulations Xingtao Zhou 1,2, Pengfei Wei 2, Xiaodong Fu 3*, Lihua Li 2 and Xiaohui Xue 4,5 1School of Civil Engineering and Architecture, Hubei University of Arts and Science, Xiangyang, China, 2Eighth Geological Brigade of Hubei, Hubei Geological Bureau, Xiangyang, China, 3State Key Laboratory of Geomechanics and Geotechnical Engineering, Edited by: Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, China, 4Key Laboratory of Advanced Transducers Faming Huang, and Intelligent Control Systems (Ministry of Education and Shanxi Province), Taiyuan University of Technology, Taiyuan, China, Nanchang University, China 5Shanxi Transportation Technology Research & Development Co., Ltd., Taiyuan, China Reviewed by: Fei Tan, The Taihongcun landslide, which was a remarkable geological disaster triggered by the China University of Geosciences, 3 China 2008 Wenchuan earthquake, had a volume of about 2 × 106 m and killed about 23 Yuan Wei, people. Through detailed field investigations, basic information of topography, geological Shijiazhuang Tiedao University, China structure and stratigraphy for the landslide were acquired and key kinetic characteristics of *Correspondence: fi fi Xiaodong Fu the landslide were identi ed. On the basis of led investigations, 2D numerical models with [email protected] discrete element method (DEM) were established to simulate the kinematics and failure process of the landslide. To ensure the validity of the dynamic calculations, the free-field Specialty section: boundary condition was developed and introduced intro the DEM models. According to This article was submitted to Environmental Informatics and Remote filed investigations and DEM simulations, the dynamic processes of the Taihongcun Sensing, landslide can be divided into four phases: fragmentation, projection motion, scraping, a section of the journal fl Frontiers in Earth Science and granular debris ow and accumulation. In addition, the parameter analysis showed fi fl Received: 15 May 2021 that the particle bond strength had a signi cant in uence on the runout distance and Accepted: 15 July 2021 landslide debris morphology. Finally, the possible mechanism of the Taihongcun landslide Published: 02 August 2021 was determined: a rock mass of poor quality provided the lithological basis for this Citation: landslide formation; a joint set J in the back scarp and a weak interlayer of carbonaceous Zhou X, Wei P, Fu X, Li L and Xue X 1 (2021) Dynamic Process and slate and shale between the upper sliding mass and the bedrock formed the rupture Mechanism of the Catastrophic boundaries of the upper source area; a strong seismic ground motion was the external Taihongcun Landslide Triggered by the 2008 Wenchuan Earthquake Based on excitation that triggered the destructive landslide event; additionally, hypermobility was Field Investigations and Discrete caused by the high elevation and topographical conditions of the landslide. Element Method Simulations. Front. Earth Sci. 9:710031. Keywords: Taihongcun landslide, field investigation, discrete element method, dynamic process, formation doi: 10.3389/feart.2021.710031 mechanism Frontiers in Earth Science | www.frontiersin.org 1 August 2021 | Volume 9 | Article 710031 Zhou et al. Dynamic Process and Mechanism Taihongcun Landslide INTRODUCTION et al., 2014; Che et al., 2016) and finite difference method (FDM) (Bouckovalas and Papadimitriou, 2005; Bourdeau and On May 12, 2008, a magnitude Mw 7.9 earthquake occurred in Havenith, 2008; Zhou et al., 2013). The continuous simulation the Longmenshan Mountains tectonic zone of Sichuan Province, methods are based on the assumption of small deformation and China. The earthquake’s epicenter was located at Yingxiu Town, displacement; therefore, using this type of approach, it is difficult Wenchuan County (31.0°N and 103.4°E), and the hypocenter was to describe large displacements along discontinuities and at a depth of approximately 19 km. Surface displacements rotations of blocks in a jointed rock mass under seismic produced by the fault rupture reached several meters, loading. The second category consists of discontinuum propagating from the epicenter for approximately 240 km methods such as discontinuous deformation analysis (DDA) along the mountain range (Fan et al., 2018). According to the (Wu and Chen, 2011; Zhang et al., 2015; Huang et al., 2016; statistical data provided by the Chinese government, this Fu et al., 2019) and the discrete element method (DEM). With an earthquake claimed the lives of more than 87,000 people and explicit scheme-based force balance solution, the DEM exhibits a injured approximately 459,000 others (Qi et al., 2010). More than high computational efficiency in the seismic analysis of large- 60,000 rock avalanches and landslides were triggered by the 2008 scale rock mass engineering. In the DEM, blocks or particles Wenchuan earthquake (Gorum et al., 2011; Wang et al., 2014), resulting from different discretizations of the domain of interest and several hundred landslide dams were formed. can lead to different approaches. The most popular block-based Landslides triggered by strong earthquakes have always been a DEMs are the commercialized UDEC and 3DEC for solving two- popular topic of discussion. The dynamics and failure and three-dimensional (2D and 3D) problems; these programs mechanisms of earthquake-induced landslides are critical to have been extensively used in seismic response analyses for rock elucidate for improving hazard prevention and mitigation engineering (Kveldsvik et al., 2009; Cui et al., 2016; Song et al., measures. Field investigations indicate that the kinematic 2018). The particle-based DEM method introduced by Cundall processes of earthquake-induced landslides are characterized and Strack (1979) simulates the mechanical behavior of a material by high speeds, long runouts, and high mobilities (Wang by representing it as an assemblage of discs (2D) and spheres et al., 2009; Yin et al., 2009; Chigira et al., 2010; Dai et al., (3D). The DEM was originally used to investigate granular 2011; Gorum et al., 2011; Tang et al., 2011; Huang et al., 2012; materials such as soils/sands and was eventually implemented Zhang and Yin, 2013; Zhang et al., 2016). Considerable kinetic in a commercial code, i.e., Particle Flow Code (PFC) (Itasca energy, high toe to rupture surface elevations, elastic energy Consulting Group Inc., 2008). To solve problems related to a rock release due to grain fragmentation, and high excessive pore mass, a bonded particle model (BPM), in which intact rocks are water pressure generated by undrained loading were represented as assemblages of cemented rigid particles, was underscored as the principal controlling factors for the long developed (Potyondy and Cundall, 2004), and a smooth joint travel distance, high speed, and high mobility (Wang et al., contact model (SJCM) was proposed to model the joints (Ivars 2009; Chigira et al., 2010; Zhang and Yin, 2013; Wang et al., et al., 2011). 2014). It was concluded that the occurrence of an earthquake- As previously documented, many earthquake-triggered induced landslide is controlled mainly by seismic, terrain, and landslides are characterized by flow-like movement, and the geological factors (Huang et al., 2012). Strong ground motion sliding material disintegrates into fragments during the high- generated by the earthquake and topographic amplification of speed movement, ultimately forming a granular deposit. The seismic waves due to features of the terrain were emphasized as particle-based DEM method simulates the geomaterial as the main triggers of rock avalanches and landslides (Havenith assemblies of rigid discs (in 2D) or spheres (in 3D) bonded at et al., 2003; Murphy, 2006; Bourdeau and Havenith, 2008; Yin their contacts and allows finite displacements, rotations and et al., 2009; Huang et al., 2012; Zhou et al., 2013). separations of the discrete particles. The failure process in the Field investigation and numerical simulation are two synthetic material can be represented by the breakage of bonds fundamental techniques for analyzing the dynamics and and propagation and coalescence of these microcracks. Therefore, revealing the possible mechanism of individual landslides the particle-based DEM is more appropriate than DDA or the induced by strong earthquakes. Through field investigation, continuum methods for simulating the dynamic failure process detailed information about a single landslide can be obtained, and kinematic characteristics of landslides triggered by such as its geological and topographical features (Has and Nozaki earthquakes. Huang et al. (2012), Tang et al. (2013), Zhou et al. 2014; Wang et al., 2014; Zhang et al., 2016; Zhuang et al., 2018). (2013), Yuan et al. (2014),andDeng et al. (2017) developed 2D DEM Furthermore, field investigation can provide evidence of the models to simulate the dynamic process of landslides triggered by dynamic processes for landslides (Zhang et al., 2011, Zhang earthquakes and explore their seismic failure mechanism. In their et al., 2016; Xu et al., 2013). Numerical simulation is an simulations, the sliding surface and bedrock were represented by wall important approach for modelling the dynamic process of elements, and the seismic ground motion histories were