Quaking in transitions- among frictional and free slipping granular system

Wei-Chih Li^1*, Cheng-En Tsai^1,3, Pai-Yi Hsiao², Jih-Chiang(JC) Tsai¹

¹Institute of Physics, Academia Sinica, Taipei, Taiwan
²Dept. of Engineering and System Science, National Tsing Hua University, Hsinchu, Taiwan
³Department of Phyiscs, National Taiwan University, Taipei, Taiwan

* Presenter:Wei-Chih Li, email:f2130831306@gapp.nthu.edu.tw

We proposed a minimal model that produces repeated quaking of soft particles under steady shearing in numerical experiments. Instead of using conventional model: fixed Coulomb friction, the tangential force weakens when the relative tangential velocity of two interaction particle exceeds a characteristic velocity. Granular flow, which is at the low-inertial limit, establishes a state diagram spanned by two axes: the average contacts per particle versus a dimensionless shear rate with the velocity weakening threshold and the grain size taken into consideration. Quaking behaviors reported previously with our recent laboratory experiments are now justified with values of this dimensionless shear rate, indicative of a transition between fully frictional “solid” and free slipping “liquid”. The mean contact number makes a connection between mechanical stability and volume fraction. These studies suggest new avenues in understanding the emergence of immediate events in granular flow, such as earthquakes and their precursor.

Keywords: granular system, quaking, velocity-weakening