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A large-scale landslide occurred at the waste dump of Dagushan open-pit iron mine in Anshan, China. The landslide caused the collapse of 8.45 × 106 m3 of waste rock with a maximum runout distance of 150 m, resulting in the burial of 7.2 × 104 m2 of the site and destruction of numerous buildings and roads. Based on field investigations, laboratory tests, and numerical simulations, the failure characteristics of the landslide were investigated and the inducing factors as well as the failure mechanism were analyzed. According to field surveys, the landslide area was divided into the traction failure area, the main sliding area, and the accumulation area. A series of in situ and laboratory tests were performed to obtain the engineering properties of the waste material and the foundation silty clay of the waste dump. Then, a conceptual model of the landslide mechanism was constructed and the failure process was divided into four stages: foundation weakening stage, shearing and dislocation stage, sliding and shearing out stage, and tractive sliding stage. Two- and three-dimensional numerical simulations were performed to clarify the landslide evolution and related triggering mechanism combining the strength reduction method with the finite difference program FLAC3D. The results show that the saturation and weakening of foundation silty clay under the action of groundwater were the trigger factors of the landslide, which resulted in the shear failure of the weak foundation, and further triggered the mass collapse and formed the large-scale landslide. The sliding surface passed through the overlying waste materials and progressed along the weak foundation of the slope. The failure pattern obtained by numerical simulations matched closely with the observations in the field. The understanding of the landslide characteristics and mechanism may offer a reference for disaster identification and stability analysis of large-scale waste dumps around the world. [ABSTRACT FROM AUTHOR]

Owing to the heavy rainfall, a landslide occurred at the Anqian Iron mine, at 18:00(UTC + 8) on November 24, 2019, in China. The landslide was about 3.0 × 104 m3 and caused damage to the road of transporting waste materials. Failure characteristics and the mechanism of this landslide were analyzed in this study. The landslide area was divided into three parts: the rear tension cracking area, the middle sliding deformation area, and the front colluvium area. A contact-free measuring technique using the new ShapeMetrix3D system was applied and 204 joints were analyzed based on equal-angle stereographic projection. Thus, a conceptual model of the mechanism of the landslide was constructed and the formation process of the landslide was divided into three stages: the first shearing and dislocation stage; the second sliding, front bulging, and rear tractive cracking stage; and the third local rock mass collapse and colluvium depositing stage. Numerical modeling was performed to discover the landslide mechanism by progressively reducing the shear strength of rock mass. The results showed that the original slope was stable, whereas heavy rainfall triggered the landslide, and the predicted failure surface matched closely the field investigations. The factor of safety obtained by real three-dimensional analyses was slightly higher than that obtained by plane problem analyses, and the difference was attributed to the three-dimensional effect of the landslide. This paper also presents the results obtained from the parametric analysis in order to understand the impact of shear strength parameters on the overall stability of the slope. [ABSTRACT FROM AUTHOR]