High-temporal-resolution quasideterministic dynamics of granular stick-slip

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.

An acoustic signature of extreme failure on model granular materials

“…The last event has a vanishing internal stress accompanied by an exceptionally large incremental axial strain of 19.2% and a jump in solid fraction of 0.018 in one single step in less than 1 s, moving I toward a higher value of about 10 ; hence the dynamic isotropic liquefaction for the slip phase 16 , crossing the jamming transition 21 and the dynamic consolidation for the stick phase 19 . Note the consistent positive delay of pore pressure outburst for all instability events, indicating a surprising counter-intuitive coupled response with systematic constant time delay 22 between the solid and liquid phases for a fully saturated two-phase mixture (Fig. 2 ).…”

“…The interpretation of the isotropic liquefaction event still remains a matter of debate; as even the simple time process of pore-water pressure dissipation in phase III 19 . The systematic changes in top cap acceleration using high-temporal-resolution measurements suggest a fast underlying modification of the granular microstructure favoured by a very inhomogeneous environment, creating a sharp increase of the pore water pressure on a timescale of milliseconds in a simple two-phase (solid and liquid) granular assembly, and followed by a dynamic consolidation towards a more compact structural rearrangement, as in stick-slip experiments in triaxial compression with shear stress 22 .…”

“…4 shows the spectrogram of or U happening within 0.25 s. The systematic delay of U (vertical black dashed line), of about 2 ms behind the changes of vertical acceleration in Fig. 2 indicates a surprising coupling response with systematic constant time delay 22 between the solid (granular skeleton) vibrated at 1175 Hz and the pore fluid (de-aired and distilled water) at only 77 Hz. Furthermore, the duration of pore fluid regular vibration, of about 0.2 s, is more than one order of magnitude longer than all others.…”

Mapping Acoustic Frictional Properties of Self-Lubricating Epoxy-Coated Bearing Steel with Acoustic Emissions during Friction Test

“…The application of polymers is crucial in tribology research due to their dynamic contact, including adhesion and deformation between the surfaces [1]. Stick-slip is an intermittent motion that consists of a stationary phase and a sliding phase and occurs in equipment such as microdrives [2], geoscience [3], dental [4], and mechanical systems [5]. Stick-slip motion is known for its tendency to cause increased wear in polymer materials [6].…”

Understanding slow compression and decompression of frictionless soft granular matter by network analysis

“…However, for larger strains, irreversible events occur that involve some dynamics (motion, rearrangement) of the particles. 23–28 In analysis of these events, in addition to classical measures (pressure, energy, coordination number), we find it insightful to consider explicitly also the force networks, describing the interparticle interactions on a scale between particles and system size. By now it is well accepted that the static and dynamic properties of these networks are closely related to mechanical properties of the whole granular sample; the examples include granular samples exposed to vibrations/tapping 29,30 or pullout of an intruder from a granular sample.…”