A discrete element numerical modeling analysis for Cone Penetration Testing (CPT) was carried out to quantify grain size effects on cone penetration tip resistance. Analyses were performed simulating a model chamber using Particle Flow Code in 2 Dimensions (PFC2D) employing the Discrete Element Method (DEM) with uniform as well as distributed grain sizes. Analyses were carried out to simulate normally consolidated granular material with vertical/horizontal overburden stress ratio (k0) equal to 0.5 and with varying relative densities. In the numerical analysis, chamber diameter, boundaries and particle diameter were varied to investigate the possible effects on the measured cone tip resistance. Some limitations of the 2-dimensional modeling vs. 3-dimensional field conditions are also discussed.; The results were compared with recent CPT research in terms of chamber diameter and boundary effects. The results are in good agreement. This research has shown that refusal of penetration can be expected when the grain to cone diameter ratio is around 1.0. Also the measured cone tip resistance will start to be influenced by the grain size when the grain to cone diameter ratio reaches about 0.3.
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