Characterization of Strong Contact Network in Gap-Graded Granular Soils

Gap-graded granular soils are used as construction materials worldwide. However, the evolution of contact network during loading process remains to be further investigated due to their heterogeneous fabric structure. The anisotropic consolidation tests and further triaxial compression tests are performed on gap-graded mixture samples by the discrete-element method (DEM), and the complex network analysis approach is utilized to describe the evolution and percolating behaviors of the network structure in granular assemblies. The effects of the initial stress ratio and particle size distribution on the macroscopic properties are analyzed, and the corresponding percolating behaviour of strong contact network is further revealed based on the complex network analysis. The threshold ξ (ratio to the mean contact force), which is the boundary between strong and weak networks, is selected to extract the strong contact network to analyze the percolation behavior. The results indicated that the initial stress anisotropy leads to an increase of contact force and the expansion of the strong contact network. The percolation thresholds increase firstly and then decrease with the increase of coarse fraction, but monotonically increase with the rise of particle size ratio. The evolution of the percolation threshold was found to be consistent with those of the macroscopic properties. The inherent relationship between the mesoscopic contact structure and the macroscopic behaviors may provide a reference for modeling the constitutive relationship of gap-graded granular soils from a new perspective.