As part of a larger project evaluating the effect of particle size distribution (PSD) and particle shape on the plug formation of open-ended piles in sand, a series of laboratory experiments have been performed. These include direct shear tests on fine, medium, and coarse sands with differing PSD and shape characteristics as well as direct shear tests on sand-aluminium interfaces. In the present study, Discrete Element Method (DEM) simulations are performed to evaluate both the PSD and particle shape effects as well as different implementation approaches to simulate particle shape in DEM simulations. In particular, the experimental results have been qualitatively compared to simulations using spherical clumps and potential surfaces for shape representation. The results are also discussed within the context of stress and strain non-uniformity in direct shear testing and provide further insight to effectively understand the actual stress conditions and the experimental interpretation of such tests. Furthermore, the comparison between spherical clumps and potential surface representation of particle shape in DEM simulations enables benchmarking algorithms in terms of their performance and accuracy. From the results, it is shown that all these factors (i.e., PSD, shape, and DEM algorithm) have a significant effect on the interpretation of direct shear tests for the determination of shear strength.