Analysis on the geological structure and characteristic of Baige landslide in Jinshajiang tectonic melange belt

The Baige landslide is located in the Jinshajiang tectonic melange belt with extremely complex geological conditions. Understanding the geological structure features of the Baige area is of crucial importance for subsequent disaster risk assessment. Following two large-scale landslide events in 2018, certain zones remain in continuous deformation, which may cause further risk of slippage. This study integrated with multi-year investigation, multi-phase UAV digital elevation models, long-term monitoring data, and detailed geological investigation, to comprehensively analyze the facility-sliding geological structure, disaster characteristics, and development trend. The results show that the rock mass composition and spatial distribution of Baige landslide are complex; the landslide body is mainly composed of gneiss, phyllite, and serpentinite. Among these, serpentinite, prone to disintegration and characterized by low shear strength, serves as a key controlling lithology in landslide deformation. The fault structures widely developed in the landslide area also play an important role in the formation and development of landslide. Landslide residual deformation areas can be divided into K1, K2, and K3 according to their spatial distribution, and the three areas can be further subdivided into 11 sub-blocks with different deformation trends. Among them, the K1-1 sub-block has a high and steep surface, while K1-4 and K1-5 contain heavily weathered serpentinite undergoing progressive deep-seated deformation, which culminated in a reactivation event on November 29, 2022. The serpentine mountain fissure continues to expand. The K2 area is controlled by carbonaceous slate and phyllite, its damage may be greater in the rainy season. The deep rock mass in the K3 area is relatively complete, with decomposition failure mainly being in the shallow layer and small possibility of deep sliding. The findings provide engineering practical references for the geological structure of landslides within the tectonic melange belt.