A new research conducted by group member Kun Wang has results in a journal article accepted by Journal of Engineering Mechanics. This research focuses on the hydro-mechanical responses of wetted granular matters at the pendular regime. By analyzing the tensorial Bishop's coefficient using Young-Laplace equation and DEM, we study the relation between the macroscopic apparent cohesion and the formation and rupture of liquid bridges. We also examine the path dependence and anisotropy of the Bishop's coefficient from the force chain evolution simulated in DEM. Further information can be found in the preprint [PDF].
The objective of this research is to use grain-scale numerical simulations to analyze the evolution of stress anisotropy exhibited in wetted granular matters. Multiphysical particulate simulations of unsaturated granular materials were conducted to analyze how the interactions of contact force chains and liquid bridges influence the macroscopic responses under various suction pressure and loading history. To study how formation and rupture of liquid bridges affect the mechanical responses of wetted granular materials, a series of suction-controlled triaxial tests were simulated with two grain assemblies, one composed of large particles of similar sizes, another one composed of a mixture of large particles with significant amount of fines. Our results indicate that capillary stress are anisotropic in both sets of specimens, and that the stress anisotropy is more significant in granular assemblies filled with fine particles. A generalized tensorial Bishop's coefficient is introduced to analyze the connections between microstructrual attributes and macroscopic responses. Numerical simulations presented in this paper indicate that the principal values and directions of this Bishop's coefficient tensor are path dependent.
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