Toward a sound understanding of a large-scale landslide at a mine waste dump, Anshan, China

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 × 10 6 m 3 of waste rock with a maximum runout distance of 150 m, resulting in the burial of 7.2 × 10 4 m 2 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.