Changing law of shear strength of typical gravel soil in Qinba Mountain area and its application in the analysis of landslide mechanism in accumulation layers

The mound landslides in the Qinba Mountain area are characterized by their large number, wide distribution, high density, and high frequency occurence, with excavation-induced landslides being particularly severe. This study focuses on the gravel soils from the mine hole landslide in the third group of Lingfeng Village, Xiaoling Town, Qinba Mountain area. Through large-scale direct shear tests conducted in the laboratory, an in-depth investigation of the gravelly soils in the study area was carried out. The variation rules of shear strength under different moisture contents, dry densities, and normal stresses were explored. Based on the results of these indoor tests, the Midas GTS NT finite element numerical simulation software was used to calculate and analyze the slope conditions before the occurrence of the landslide. Simulations were conducted to analyze the changes in stress, displacement, and stability of the slope after excavation and under two working conditions: post-excavation and post-excavation coupled with rainfall. Finally, the mechanism of typical excavation-induced landslides in stockpiles is summarized based on these findings. It was found by numerical simulation: human engineering activities, i.e., excavation of the toe of slopes and heavy rainfall occurring in the area, are the main triggering factors for landslides: the deformation pattern of typical excavation-induced landslides in the Qinba Mountains can be summarised as: traction-creep-slip type.The research results can provide valuable reference for the prevention and control of excavation-induced landslides in accumulation layers in the Qinba Mountain area.