Effect of disordered pore distribution on the fracture of brittle porous media studied by bonded DEM

Abstract

The mechanical properties of geo-materials, porous media, and cementing materials are inherently variable, owing to the presence of pores, cracks, and other microscale heterogeneities, known as Griffith flaws. In this study, we focused on the influence of disordered pore distribution on the mechanical properties of bonded granular materials and performed simulations of uniaxial tensile testing through 2D Discrete Element Method (DEM). The sample was modeled in the form of an agglomeration of elementary balls with breakable bonds, while disordered pores were introduced by deleting a certain number of elementary balls from the initial dense ordered packing. We defined the pore disorder parameter as Dp, which specifies the degree of disorder, and applied uniaxial tension to various samples with different Dp. The simulation results demonstrated that the failure strength is inversely proportionate to the level of porosity and Dp, and that the heterogeneity of stress transmission also increases with Dp. The reduction of tensile strength in a highly disordered specimen (Dp = 2.0) reached its maximum value when the porosity was 0.274, while the reduction of the tensile stiffness dominated when the porosity was 0.339. Near the percolation threshold (referring to the porosity when strength or strength becomes zero), φc=0.527, both strength and stiffness were well described by the percolation theory. In addition, larger Dp lead to higher stress concentration, causing greater uncertainty of the failure strength. These findings help us to understand the influence of structural disorder over the mechanical properties of disordered porous materials.

Keywords

• Discrete element method
• Pore distribution
• Brittle porous media
• Weibull statistics
• Disorder