REVITALIZATION MECHANISM AND THREAT RANGE PREDICTION OF LONGWUXISHAN ANCIENT LANDSLIDE GROUP, QINGHAI PROVINCE

Tongren City of Qinghai Province is located in the northeast corner of the Qinghai-Tibet Plateau,and located in the junction of the West Qinling orogenic belt and the North Qilian orogenic belt. Since the Miocene,the study area has experienced several times of intermittent geological upthrow and planation,the river valley has been strongly eroded. Under the coupling effect of internal and external stresses,there are many large-extra ancient landslides on banks of Longwu River. In recent years,affected by global warming,there are obvious signs of deformation in five ancient landslides in this area,sone old cracks have been expanded obviously,many new cracks have appeared. In this paper,the Longwuxishan ancient landslide group on the left bank of Longwu River in Tongren City is taken as the research object. The paper analyzes the development and distribution,deformation characteristics,revitalization mechanism and movement characteristics of the Xishan ancient landslide group with the help of field investigation,drilling,laboratory experiment and numerical simulation. The results indicate that:(1)The strong uplift of neotectonics and the incised valley of the Longwu River are the main controlling factors for the formation of ancient landslides; (2)Field investigation found that the recent deformation of the Xishan ancient landslide group is mainly concentrated on the No. 5,No. 7,No. 9,No. 10,No. 11 and No. 12 landslides. There are many terracettes and tension fissures on the slope surface; (3)Rainfall is the controlling factor for the revitalization of ancient Longwuxishan landslide group,the deformation failure mode is sliding and fracturing; (4)The numerical simulation result shows that the distance of landslide migration is mainly from 50 m to 75 m,the average thickness of the accumulation area is from 12 m to 18 m. At present,Xishan ancient landslide group is becoming a serious threat to the safety of Tongren County.