Failure mechanism and treatment of mine landslide with gently-inclined weak interlayer: a case study of Laoyingzui landslide in Emei, Sichuan, China

The landslide of mine is of great harm and wide influence, which can easily cause huge economic losses and endanger the life safety of workers. Therefore, landslide failure mechanism and more efficient landslide treatment methods have been the focus of landslide research. Laoyinzui landslide with a volume of 250,000 m³ occurred along the gently inclined weak interlayer at 6:00 (UTC + 8) on 5 January 2019 in Huangshan Limestone Mine, Emei City, Sichuan Province, China. The deformation history and failure mechanism of the landslide were analyzed based on the field investigation and geological conditions of landslide area. The treatment method of using excavators to remove all sliding body within the arm length by excavating the small-bench in the bedrock was proposed. The slope stability after treatment was analyzed based on the monitoring data. The results showed that the landslide was triggered by rainfall and earthquake after long-term creep deformation under the action of various factors. Weak interlayer was the potential sliding surface of landslide. The tensile cracks at the back edge of the landslide and the joint fissures and karst caves of the upper limestone provided convenient conditions for rainwater infiltration. Mining activities, including excavation and blasting, resulted in deterioration of mechanical properties of rock mass. Rainfall was the main trigger for the landslide. Water accumulated in weak interlayer, leading to increase of pore water pressure and decrease of anti-sliding force. Earthquake was the trigger for the landslide, which resulted in the reduction of rock mass structural strength. The Laoyingzui landslide consisted of two stages. First, a traction landslide of + 825 m–915 m occurred, and then a push landslide of + 725 m–+ 825 m occurred under the compression of the upper rock mass. The slope displacement was small and the deformation tended to be stable. The treatment method was safe and efficient. This paper can provide reference for the failure mechanism research and treatment of similar landslides.