2D DEM-LBM modelling of localized hydraulic failure within a cemented granular layer
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In hydraulic earthworks, such as dams or embankments, there is a risk of erosion that can affect cemented granular materials. The specificity of these materials is due to the presence of solid bonds connecting the soil particles together. The present contribution focuses on a multi-scale approach to investigate numerically the hydro-mechanical destabilization of such materials. To this end, we utilized a homemade 2D numerical code that incorporates a combination of Lattice Boltzmann (LBM) and Discrete Elements (DEM) methods including a cementation model [1]. The latter was developed based on micro-mechanical experiments [2] and was adapted from 3D to 2D. It defines a bond strength and links the micro-tensile force to the shear force and to the bending and torsion (only in 3D) moments. We performed a parametric study on the hydro-mechanical destabilization of a cemented granular layer by varying the particle diameter, the bed sample height, and the bond strength. For a given set of parameters, the flow rate, injected locally at the bottom of the soil layer, is progressively increased till critical conditions are reached. Somehow reminiscent to companion experiments, the phenomenology has revealed several regimes: (i) a stable regime where only a fraction of the solid bridges can eventually be ruptured, (ii) a fracture scenario where the cemented bed gets destabilized through nearly symmetric cracks starting at the inlet, (iii) a fluidized chimney scenario where localized grain destabilization occurred at the inlet in a manner rather similar to purely granular materials, and (iv) a mixed scenario that combines the previous two others. The influence of both inlet flow rate and bond strength on the failure modes will be finally discussed using phase diagrams.
