The Geophysical Characteristics And Stability Analysis Of The Typical Large-giant Ancient Landslide In The Minjiang River Valley In Western Sichuan Province

The Minjiang River Valley area in Western Sichuan is influenced by many kinds of internal and external dynamic forces such as topography,geological structure,earthquake,rainfall and human engineering activities.The landslides have many types and complex triggering mechanism,and a series of large giant paleo landslides are developed.Most landslides have the characteristics of plugging the river,the sliding surface is buried deeper and so on.They are characterized by high frequency,strong destructive power,huge losses,rapid and violent occurrence.Practice shows that the distribution characteristics of resistivity can reflect the distribution of strata lithology,and can qualitatively describe the shape and location of landslide surface.On the basis of remote sensing interpretation and field investigation,high density electrical method and resistivity sounding method have been adopted to improve the defects of the traditional high density electrical measurement lines at both ends of the line.The spatial structure of the typical large scale landslides,such as the landslides and the landslides of tuancun landslides,has been explored and analyzed.The spatial structure of the ancient landslides and the characteristics of the slide zone are effectively determined.Combined with large-scale direct shear test,the stability of ancient landslide in Tujia village under different working conditions was analyzed by numerical simulation analysis.Through the above work,we get the following research results:(1)Using the conventional electrical sounding method to complement the high-density resistivity method,the complete spatial structure characteristics of landslide can be effectively obtained.From the results of geophysical inversion,it can be seen that the electrical properties of the loess,gravel soil and underlying bedrock on the surface of the landslide are very different,so the easy to distinguish the vertical structure is beneficial to determine the depth of the sliding surface and determine the position of the sliding surface.(2)The sliding surface of the ancient landslides in the Minjiang River Valley in Western Sichuan is mostly located in the unstable electrical layer between the high and low resistance phases,and the front of the landslide is mostly located in the place where the unstable electrical layer is thinner and converge.Among them,there is a trap of low resistivity anomaly in the map of the geophysical inversion of the gas,which is an ancient channel,which is in accordance with the results of drilling,and its buried depth is about 56~96m.The discovery of the ancient river course is of great significance to the study of the formation mechanism of the ancient landslide in the temple.(3)The stability of the ancient landslide in unity village is analyzed by FLAC~3DD simulation and large direct shear test,and the stability of the landslide is obtained under different working conditions.The results show that the ancient landslides in the unity village are easily sliding again under heavy rainfall conditions,and the landslide of the ancient landslides from the slope foot to the top of the slope is shown to show the landslide.There is a multilevel sliding surface in the body.