Abstract
We report high-temporal-resolution observations of the spontaneous instability of model granular materials under isotropic and triaxial compression in fully drained conditions during laboratory tests representative of earthquakes. Unlike in natural granular materials, in the model granular materials, during the first stage of the tests, i.e., isotropic compression, a series of local collapses of various amplitudes occurs under random triggering cell pressures. During the second stage, i.e., shearing under triaxial compression, the model granular samples exhibit very large quasiperiodic stick-slip motions at random deviatoric triggering stresses. These motions are responsible for very large stress drops that are described by power laws and are accurate over more than 3 decades in logarithmic space. Then, we identify the quasideterministic nature of these stick-slip events, assuming that they are fully controlled by the cell pressure and solid fraction. Finally, we discuss the potential mechanisms that could explain these intriguing behaviors and the possible links with natural earthquakes.
Highlights
We report high-temporal-resolution observations of the spontaneous instability of model granular materials under isotropic and triaxial compression in fully drained conditions during laboratory tests representative of earthquakes
We provide the first assessment of quasideterministic dynamics of stick-slip motion occurring in slowly sheared triaxial compression e xperiments[17,35,36,37,38] performed on model granular media
We explore the role of pore pressure outbursts; while pore pressure outbursts are not a causative mechanism, they lead to a rational explanation of stick-slip events induced by drained triaxial compression with dynamic consolidation under constant deviatoric stress
Summary
We report high-temporal-resolution observations of the spontaneous instability of model granular materials under isotropic and triaxial compression in fully drained conditions during laboratory tests representative of earthquakes. The discovery of very large stick-slip motions in loose and saturated model granular materials under drained triaxial compression[17] presents a unique opportunity to elucidate some details of the mechanisms of catastrophic earthquake-like events in the laboratory, especially the fast outburst of pore fluid pressure, which is a distinctive signature of these instabilities. These intriguing experimental observations raise many questions about their origins and interpretation. The presence of pore fluid in a fully saturated simple two-phase granular assembly is essential in creating the largest laboratory earthquakes, which result in complete destruction of the granular structure[39]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
