Steady state of solid-grain interfaces during simulated CPT

It has recently been shown (Arroyo et al. [1]) that 3D DEM models are able to reproduce with reasonable accuracy the macroscopic response of CPT performed in calibration chambers filled with sand. However, the cost of each simulation is an important factor. Hence, to achieve manageable simulation times the discrete material representing the sand was scaled up to sizes that were more typical of gravel than sand. A side effect of the scaled-up discrete material size employed in the model was an increased fluctuation of the macro-response that can be filtered away to observe a macroscopic steady-state cone resistance. That observation is the starting point of this communication, where a series of simulations in which the size ratio between penetrometer and particles is varied are systematically analyzed. A micromechanical analysis of the penetrometer-particle interaction is performed. These curves reveal that a steady state is arrived also at the particle-cone contact level. The properties of this dynamic interface are independent of the initial density of the granular material.