9:45 AM - 10:00 AM
[SSS05-14] Packing structure of spherical particles following a power size distribution for modeling the fault gouge
Keywords:fault gauge, grain size
Particles following a power size distribution are ubiquitous in nature. This is because they spontaneously arise as a result of fracture or critical phenomena. The most well-known example is the formation of particles by impact fracture, but failure under compression has also been found to produce particles that follow a power size distribution in simulations of two-dimensional spherical particles (Ben-nun, Einav and Tordesillas, 2010). The particles that make up the fault gouge filling fault surface are one of the most important examples of particles with a power size distribution. They follow a power size distribution over a range of 1 μm to 1 mm. In earthquakes, the gouge may govern the friction law of the fault, and simulations with two-dimensional spherical particles with a discrete size distribution similar to the power law have attempted to understand the dynamic friction forces (Morgan and Boettcher, 1999). Thus, the packing of particles with power size distributions may play an important role in deformation in earthquakes.
The size of particles appearing in the fault gouge can be approximated by a power distribution with cutoffs, which distribution is determined by exponent and the range between the cutoffs. The large cutoff is bounded by the width of the fault and small cutoff is limited by the condensation force as a powder. The exponent is expected to vary depending on the fracture process, and is known to be in the range of approximately 3.6 to 4.0 (e.g. Chester, Evans and Biegel, 1993). In order to clarify the dynamics of earthquakes, we need to focus on exponent, because the physical properties are determined only by exponent if the cutoff width is set sufficiently large.
Against this background, we approached the understanding of the geometrical structure by constructing a random packing by simulation and experiment with two-dimensional circular particles following power size distributions (Shimamoto, Yanagisawa, 2023). It was found that the number of mechanically unconstrained particles increases rapidly when exponent falls below 2, but their area fraction remains almost constant. Furthermore, the packing was found to have a common network structure in the region of exponent less than 3, which commonality originates from self-similarity. In this presentation, we will discuss the structure formed by such densely packed particles with power size distribution and also report the phenomena revealed so far under macroscopic deformation.
Reference
Ben-Nun, O., Einav, I., & Tordesillas, A. (2010). Force attractor in confined comminution of granular materials. Physical Review Letters, 104(10), 108001.
Morgan, J. K. (1999). Numerical simulations of granular shear zones using the distinct element method: 2. Effects of particle size distribution and interparticle friction on mechanical behavior. Journal of Geophysical Research: Solid Earth, 104(B2), 2721-2732.
Chester, F. M., Evans, J. P., & Biegel, R. L. (1993). Internal structure and weakening mechanisms of the San Andreas fault. Journal of Geophysical Research: Solid Earth, 98(B1), 771-786.
Shimamoto, D. S., & Yanagisawa, M. (2023). Common packing patterns for jammed particles of different power size distributions. Physical Review Research, 5(1), L012014.
The size of particles appearing in the fault gouge can be approximated by a power distribution with cutoffs, which distribution is determined by exponent and the range between the cutoffs. The large cutoff is bounded by the width of the fault and small cutoff is limited by the condensation force as a powder. The exponent is expected to vary depending on the fracture process, and is known to be in the range of approximately 3.6 to 4.0 (e.g. Chester, Evans and Biegel, 1993). In order to clarify the dynamics of earthquakes, we need to focus on exponent, because the physical properties are determined only by exponent if the cutoff width is set sufficiently large.
Against this background, we approached the understanding of the geometrical structure by constructing a random packing by simulation and experiment with two-dimensional circular particles following power size distributions (Shimamoto, Yanagisawa, 2023). It was found that the number of mechanically unconstrained particles increases rapidly when exponent falls below 2, but their area fraction remains almost constant. Furthermore, the packing was found to have a common network structure in the region of exponent less than 3, which commonality originates from self-similarity. In this presentation, we will discuss the structure formed by such densely packed particles with power size distribution and also report the phenomena revealed so far under macroscopic deformation.
Reference
Ben-Nun, O., Einav, I., & Tordesillas, A. (2010). Force attractor in confined comminution of granular materials. Physical Review Letters, 104(10), 108001.
Morgan, J. K. (1999). Numerical simulations of granular shear zones using the distinct element method: 2. Effects of particle size distribution and interparticle friction on mechanical behavior. Journal of Geophysical Research: Solid Earth, 104(B2), 2721-2732.
Chester, F. M., Evans, J. P., & Biegel, R. L. (1993). Internal structure and weakening mechanisms of the San Andreas fault. Journal of Geophysical Research: Solid Earth, 98(B1), 771-786.
Shimamoto, D. S., & Yanagisawa, M. (2023). Common packing patterns for jammed particles of different power size distributions. Physical Review Research, 5(1), L012014.