Experimental study of shear deformation of the medium formed by the massif of ribbed grains

Abstract

The approach to the study of the seismically active zone as an open system that is in a state of self-organized criticality is becoming increasingly used in modern research. The models used in this approach should reflect the most characteristic features of such media: discreteness, nonequilibrium, nonlinear and nonlocal nature of interactions. In this paper, the medium is modeled by a granular massif with ribbed grains. Three different massifs are used in the research. Within one massif, all grains are identical, while grains from different massifs differ in shape (cubic or irregular ribbed) and characteristic size.
 A number of experiments of shear deformation of such granular massifs were carried out in order to study the influence of the shape and size of grains on the statistical charac-teristics of the process. The influence of the stress state on the deformation properties of these media was also studied. The experiments proved the qualitative similarity of the behavior of different granular media. Obtained experimentally force jumps, represen-ting the reaction of the granular medium to shear deformation, obey the distributions in the form of power dependencies. However, the magnitudes of the forces arising in the massifs depend on the grain shape and size as well as the stress state in the massifs. The experiments with shear deformation of the granular media under the external action of small impulse stresses have shown that such action causes a smoother, devoid of sharp jumps, deformation. External perturbations shift the distribution of the force jumps towards smaller values, leaving their exponents unchanged.
 The analysis of experimental results using nonadditive statistical mechanics confirmed the presence of long-range correlations in the massif of ribbed granules during its shear deformation.

On the similarity of shear deformation of a granular massif and a fragmented medium in the seismically active area

“…In particular, the deformation of granular media occurs intermittently and it is accompanied by the generation of acoustic perturbations. These stochastic perturbations obey the same statistical laws as earthquakes: Gutenberg-Richter law, Omori's law, the universal low for distribution of intervent times between avalanches [Geller et al, 2015;Lherminier et al, 2019;Mykulyak et al, 2019bMykulyak et al, , 2021Kumar et al, 2020].…”