Numerical inversion of the motion process of high rockslide body considering block size effect: A case study of Pusa rockslide in Nayong County, China

Abstract

[Objective] Rockslide disaster caused by slope instability of reverse gently inclined layered jointed fragmentation rock mass structure is one of the common types of mountain disasters. It is of practical significance to explore the process of instability and failure for disaster prevention and control. Taking the ‘8.28 Pusa collapse' in Guizhou as the research object, the deformation history and rock mass structure characteristics of Pusa rockslide were analyzed. [Methods] Using the topographic mapping data, a three-dimensional geological model was constructed, and the block size of the rockslide accumulation body was counted by the Particles(Pores) and Cracks Analysis System(PCAS). Four different block sizes of 0.5 m, 2.0 m, 3.5 m and 5 m were set to invert the rockfall movement process of the Pusa rockslide. [Results] The research shows that:(1)The block size of the rockslide accumulation block ladder in Pusa is mostly concentrated between 1~2 m;(2)Under different block size conditions, the maximum velocity, maximum energy, maximum distance and maximum height of the broken block reach 74.55 m/s, 2.3×104 kJ, 667 m and 107 m respectively, and the particle size has different degrees of influence on the motion characteristics of rockfall.(3)The velocity of the third zone changes abruptly at the step of the accumulation zone, and the velocity decreases rapidly from 30 m/s to about 20 m/s. [Conclusion] Block size affects rockfall movement; The movement mode of rockfall in the process of migration is “free fall—rolling(collision/impact bounce)—rolling(collision/sliding friction)”; Micro-topography affects rockfall movement. The research ideas and method of this paper can be used for the risk of other landslide disasters.

Keywords

Fragmentation rock mass structure / Rockslide / Block size / Motion characteristics / Micro-topography