Stability of monomer-dimer piles

Area of Science:

• Granular physics
• Materials science
• Statistical mechanics

Background:

• Understanding the stability of granular materials is crucial in various fields, from geology to engineering.
• The behavior of granular piles is influenced by factors like grain size, shape, and packing density.

Purpose of the Study:

• To experimentally and theoretically investigate the effect of adding dimer grains to monodisperse spherical grains on pile stability.
• To quantify the relationship between the weight fraction of dimer grains and the maximum static angle of stability and packing fraction.
• To understand the micro-scale mechanisms governing the enhanced stability of granular piles with mixed grain compositions.

Main Methods:

• Experimental preparation and tilting of granular piles composed of spherical and dimer grains.
• Theoretical analysis to model the stability and packing fraction of the mixed granular systems.
• Measurement of the maximum static angle of stability (tan theta(c)) and grain packing fraction (Phi).

Main Results:

• The maximum static angle of stability (tan theta(c)) increased from 0.45 to 1.1 as the dimer grain fraction (nu(d)) increased from 0 to 1.
• The grain packing fraction (Phi) decreased from 0.58 to 0.52 with the addition of dimer grains.
• Pile stability is primarily controlled by surface grains and their interaction with local traps, which are enhanced by the presence of dimers.

Conclusions:

• The addition of dimer grains significantly enhances the static stability of granular piles.
• The increased stability is attributed to the improved trapping of grains on the pile surface due to the presence of dimers.
• Further characterization of surface roughness is needed for a complete quantitative understanding of the observed phenomena.