[M-IS07] Geophysical particulate gravity current

[MIS07-P03] Dynamics of granular systems in landslides and the effect of cohesive energy

*Satoshi Katsuyama¹, Tetsuo Yamaguchi¹ (1.Graduate school of Agricultural and Biological Sciences, The University of Tokyo)

Keywords:granular, landslides, cohesion

It is known that a phenomenon called apparent reduction of friction, in which the ratio of the initial height H of rock masses to its slide distance L (effective coefficient of friction) H/L becomes smaller than the coefficient of friction μ between rock masses and the host rock, occurs in landslides[1]. In the past, many mechanisms have been proposed to explain this phenomenon, such as lubrication by water or acoustic fluidization [2], but they have not been elucidated. Therefore, in this study, we focus on the motion of rock masses as it is crushed during a landslide and perform numerical simulations using the discrete element method (DEM). As a result, we were able to reproduce the behavior of rock masses being crushed. Moreover, when we changed the cohesive force between rock particles, a new behavior was found: when the cohesive force is large, the effective coefficient of friction is equal to μ, and when the cohesive force is small, the effective coefficient of friction is small, but in between the two values, it is larger than μ. These results are thought to be caused by the fact that the fracture energy consumes part of the kinetic energy as rock masses undergoes fracture while continuing its sliding motion.

References
[1] Brandon C. Johnson, Charles S. Campbell , and H. Jay Melosh J, "The reduction of friction in long runout landslides as an emergent phenomenon" Res. Earth Surf., 121, 881–889, (2015).
[2]Collins, G. S., and Melosh, H. J, "Acoustic fluidization and the extraordinary mobility of sturzstroms" J. Geophys. Res., 108(B10), 2473,(2003).