Research On The Relationship Between Large-scale Ancient Landslide And River Terraces In The Middle Section Of Upper Reaches Of Minjiang River

In recent years,a number of large-scale landslides have occurred in the upper reaches of the Minjiang River in Sichuan Province.The large-scale Landslide Damming Events have caused serious casualties and property losses.At the same time,there are many widely distributed ancient dammed lakes are large scale,which have the characteristics of long duration and seriously harmful.The ancient dammed lake also has a major impact on the geomorphology and water system evolution in the upper reaches of the Minjiang River.Therefore,it is of great significance to study the the investigation of ancient landslides and collapse characteristics,the response analysis of landslides to river terraces and the reconstruction of paleoenvironment in this area,and to monitor the deformation of landslides and prevent geological disasters.In this paper,based on the construction of Monitoring and early warning platform for geological hazard chain in strong earthquake areas.On the basis of data collection and field investigation of ancient landslides and river terraces in the upper and middle reaches of Minjiang River,this paper analyses the development relationship between them in Maoxian County.Obtained the following conclusions:(1)The development of river terraces in the upper reaches of Minjiang River has obvious sectional feature,and it is mainly caused by the multiphase climatic change fluctuations and tectonic movement.The bursting process of barrier lake is an important controlling factor affecting the development of river terraces in alpine gorge region.(2)Large-scale ancient landslides occurred mostly in the Dixi-Maoxian section during the period of 20-30 ka B.P.Among them,the ancient landslide occurred at 20 ka B.P.was mainly caused by climate fluctuation and the ancient landslides occurred at 30 ka B.P.may be mainly controlled by tectonic activities(earthquakes).(3)The formation of river terraces in Dixi-Maoxian section is closely related to ancient landslides and barrier lake deposits.Landslides and barrier lake deposits provide material basis for the formation and development of multi-level terraces.The large-scale development of ancient landslides is caused by terrace damage after erosion base cutting.This will also have certain significance to the prediction of the occurrence period of the landslide in the future.It is suggested to strengthen the monitoring of the deformation of the ancient landslide body and the evaluation of the revived type of the ancient landslide accumulation body in the Songpinggou-Diexi-Mao county of minjiang river.(4)Through field investigation and deformation monitoring of Tizicao landslide in the upper reaches of Minjiang River,it is found that the material of the landslide is mainly gravel soil.Monitor indicates that different degrees of slip.The middle and rear part of the sliding mass are loose.It is possible to further landslide under rainfall or strong earthquake.It is suggested to strengthen the deformation monitoring and engineering control to prevent the occurrence of the disaster chain,such as landslides and barrier lakes.