This study presents analytical and experimental approaches to identify packing factors for polydisperse granular materials that maximize structural strength. The findings indicate that structural strength depends not only on the packing density but also on the particle-size distribution. A higher percentage of large particles correlates with greater structural strength, even for packings with identical density values. Therefore, this study proposes that the criterion for optimal packing should prioritize the maximum structural strength instead of the maximum packing density. This criterion is derived from proposed coordination numbers for polydisperse granular materials, which account for both the compaction degree and the proportion of particles of varying sizes. Physical experiments were conducted to measure the densities of packings with different particle-size distributions, and the experimental results were compared with analytical simulations using the discrete-element method. These comparisons indicate qualitative agreement between experimental and analytical data.

ABSTRACT
1. Introductuon
2. Formulation of the discrete element method
    2.1. Equations of motion
    2.2. Equations of motion
3. Methodology
    3.1. Computer simulation procedure
    3.2. Experimental variations of polydispersegranular material packings
4. Results and Discussion
    4.1. Optimality criterion for a dry granular packing
    4.2. Experimental Packing Density
    4.3. Stability of Granular Material
    4.4. Computational Packing Density
5. Conclusions
ACKNOWLEDGMENTS
REFERENCES

• Shoukat Touqeer(Ph.D. Candidate, Korea Institute of Civil Engineering and Building Technology School (UST))
• Kim Yeon Tae(Research Specialist. Korea Institute of Civil Engineering and Building Technology) | 김연태 Corresponding author
• Yoo Pyeong Jun(Senior Research Fellow, Korea Institute of Civil Engineering and Building Technology) | 유평준
• Kim Jongsik(Senior Researcher, Korea Institute of Civil Engineering and Building Technology) | 김종식