Contact Force Distribution and Induced Anisotropy in Granular Materials under Biaxial Test

Abstract:

A 2-dimensional granular assembly, subjected to isotropic consolidation and biaxial compression, is simulated by applying discrete element method and the particle flow code of PFC2D. The contact force network and distribution are examined and compared to an analogous photoelastic experiment carried out by other studies. The current study shows that the assembly undergoes dilatation and strain-softening after peak strength, and the coordination number (average contact number of particles) increases a little in the initial stage of strain hardening followed by a sharp dropping before the onset of softening. This is correlated with the contact force chain establishment and the evolution of structural anisotropy. The distribution of the normal force and the ratio of tangential to normal force for both the isotropically compressed and sheared stages indicates that the strong normal contacts are crucial for the force chain transmitting stress through assembly. The angular distribution of the contact forces supported this point and could help visualizing the induced anisotropy. These issues are vital for gaining a deeper understanding of the macroscopic behavior of granular material from microscopic analysis.

• Periodical: Advanced Materials Research (Volumes 446-449)
• Pages: 1927-1934
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.446-449.1927
• Online since: January 2012
• Authors: Min Yun Hu, Qiao Hao Chen, Ying Shen, Xiao Wu Tang
• Keywords: Biaxial Test, Contact Force, Induced Anisotropy, Particle Flow Code

References

[1] Cambou B, Jean M, Rajai. (eds). Micromechanics of Granular Materials [M]. New York: John Wiley & Sons, Inc., 2009.

[2] ANTONY S J, Evolution of force distribution in three-dimensional granular media [J]. Physical Review E 63: 011302, 2000.

[3] KRUYT N P. Contact forces in anisotropic frictional granular materials [J]. International Journal of Solids and Structures, 40: 3537–3556, 2003.

DOI: 10.1016/s0020-7683(03)00148-3

[4] BOSKOL J T, TORDESILLAS A. Evolution of Contact Forces, Fabric, and Their Collective Behavior in Granular Media under Deformation: a DEM Study [J]. ASCE 2006.

DOI: 10.1061/40830(188)34

[5] PETERS J F, MUTHUSWAMY M, WIBOWO J, AND TORDESILLAS A. Characterization of Force Chains in Granular Material [J]. Physical Review E 72: 041307-1, 8, 2005.

DOI: 10.1103/physreve.72.041307

[6] Minyun Hu, O'Sullivan C, Jardine R R, & Mingjing J. Stress-induced anisotropy in sand under cyclic loading [J]. Granular Matter, 12: 469-476, 2010.

DOI: 10.1007/s10035-010-0206-7

[7] MAJMUDAR T S, BEHRINGER R P. Contact force measurements and stress-induced anisotropy in granular materials [J]. Nature, 435(23): 1079–1082, 2005.

DOI: 10.1038/nature03805

[8] Itasca Consulting Group Inc. Particle Flow Code in 2 Dimensions, PFC2D Version 3.1 [M]. Minneapolis: Itasca Consulting Group Inc, 2006.

[9] BATHURST R J, ROTHENBURY L. Investigation of micromechanical features of idealized granular assemblies using DEM [J]. Engineering Computations, 1992, (9): 199–210.

DOI: 10.1108/eb023859