Study On The Formation Mechanism Of Xiaobiangou Landslide In Yanan

Yan'an is located in the hinterland of the loess plateau,with a wide range of ravines and sparse vegetation,and the loess is widely deposited in the rugged and undulating ancient terrain of the Jurassic bedrock.Due to rainfall river erosion and other factors,a large number of landslides have been developed in the area,especially,the loess-bedrock interface landslides always have huge scale and serious demage.With the improvement of local social and economic level,coupled with the lack of understanding of landslide disasters,a large number of construction are carried out on the body of the old landslides,which makes the local old landslides reactive and threaten the safety of people's lives and property in the area.As Xiaobiangou landslide is a typical representative landslide of many loess-bedrock interface landsildes in Yan'an area,the research on the formation mechanism of this landslide is not only theoretically significant,but also provides reference for the prevention and control of the type of landslide in Yan'an area.Based on the lollected data ih the region and the field investigation,combined with the the corresponding soil engineering test,landslide physical model test and numerical simulation are carried out to analyze the formation mechanism of the Xiaobiangou landslide,The main results are as follows:(1)Through the investigation,exploration and engineering geological survey of Xiaobiangou landslide,it is concluded that the Xiaobian Gully landslide is formed in different periods,which can be divided into the old landslide and the new landslide.(2)Combined with the geological environment condition and the slope structure of the Xiaobiangou landslide,it is concluded that the formation of the old landslide is mainly affected by river erosion and rainfall.According to this,a landslide physical model test is designed to reproduce the formation process of the old landslide.The formation process of the old landslide is analyzed by the slope softening stage,creep deformation stage and failure slip stage(3)The formation of the Xiaobiangou new landslide is mainly affected by the excavation of the slope.Engineering excavation makes the unloading cracks gradually expanded,and finally conecte to the sliding zone of the old landslide to form a new sliding zone.With the anti-slip soil was excavated,the landslide formed.(4)The stability of the new landslide during the excavation is analyzed by the transfer coefficient method and the finite difference method.With the excavation progress,the stability of the new landslide is decreasing.The finite difference method is used to analyze the displacement and the yield state of Xiaobiangou slope during the excavation.The formation process of the new landslide is analyzed in depth.