Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China

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Vol15 No.2: 364-379

Title】Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China

Author】JIANG Shu1*; WANG Yi-feng 2; TANG Chuan 3; LIU Ke 2

Addresses】1 Postdoctoral Research Station, China Three Gorges Corporation, Beijing 100038, China; 2 Wudongde Project Construction Department, China Three Gorges Projects Development Co., Ltd, Luquan 651500, China; 3 State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China

Corresponding author】jiangshucugb@gmail.com

Citation】Jiang S, Wang YF, Tang C, et al. (2018) Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China. Journal of Mountain Science 15(2). https://doi.org/10.1007/s11629-017-4473-1

DOI】https://doi.org/10.1007/s11629-017-4473-1

Abstract】Long-term kinematic research of slow-moving debris slide is rare despite of the widespread global distribution of this kind. This paper presents a study of the kinematics and mechanism of the Jinpingzi debris slide located on the Jinsha river bank in southwest China. This debris slide is known to have a volume of 27×106 m3in active state for at least one century. Field survey and geotechnical investigation were carried out to define the structure of the landslide. The physical and mechanical properties of the landslide materials were obtained by in-situ and laboratory tests. Additionally, surface and subsurface displacements, as well as groundwater level fluctuations, were monitored since 2005. Movement features, especially the response of the landslide movement to rainfall, were analysed. Relationships between resisting forces and driving forces were analysed by using the limit equilibrium method assuming rigid-plastic frictional slip. The results confirmed a viscous component in the long-term continuous movement resulting in the quasi-overconsolidated state of the slip zone with higher strength parameters than some other types of slow-moving landslides. Both surface and subsurface displacements showed an advancing pattern by the straight outwardly inclined (rather than gently or reversely inclined) slip zone, which resulted in low resistance to the entire sliding mass. The average surface displacement rate from 2005 to 2016 was estimated to be 0.19~0.87 mm/d. Basal sliding on the silty clay seam accounted for most of the deformation with different degrees of internal deformation in different parts. Rainfall was the predominant factor affecting the kinematics of Jinpingzi landslide while the role of groundwater level, though positive, was not significant. The response of the groundwater level to rainfall infiltration was not apparent. Unlike some shallow slow-moving earth flows or mudslides, whose behaviors are directly related to the phreatic groundwater level, the mechanism for Jinpingzi landslide kinematics is more likely related to the changing weight of the sliding mass and the downslope seepage pressure in the shallow soil mass resulting from rainfall events.

Keywords】Kinematics; Slow-moving debris slide; Shear strength; Rainfall infiltration; Viscous component