DEM STUDY OF INVERSE GRADING PHENOMENON IN LANDSLIDE DEPOSITS

The investigation of landslide disasters shows that for large high-speed long-distance landslides, there is the deposit phenomenon of inverse grading. This paper attempts to reveal the mechanism and influencing factors of deposit phenomenon of inverse grading in large landslide. It studies the influence of fractal dimension, landslide volume and slide length on the relative movement of particles with different sizes with the means of DEM. Furthermore, Jiweishan landslide is simulated and the inverse grading phenomenon is reproduced. The results show the follows. In the process of sliding, particles of different sizes are formed due to particle breakage. Under the effect of particle sorting mechanisms, smaller particles move to the lower part of the landslide through the pores among larger particles. Larger particles overpass the adjacent smaller ones under shear stress. Finally an inverse grading structure is formed in landslide deposits. The particle separation process is mainly controlled by the force of random fluctuating sieve and shear action and affected by the particle size and overburden pressure. The larger the fractal dimension is, and the larger the overburden pressure is, the smaller the degree of particle separation is, and the less obvious the deposit phenomenon of inverse grading is.