The problems encountered in geomechanics are usually three-dimensional in nature, where soil elements are subjected to principal stress rotations. The influence of such principal stress rotation is often explored in the laboratory by conducting hollow-cylinder and true-triaxial tests or conventional axisymmet-ric triaxial tests subjected to both compression and extension type stress-paths. In order to understand the particle-level mechanism of specimen deformation under such loading conditions, Discrete Element Method (DEM) has been used widely. Generally, laboratory test specimens contain millions of particles, and considering these many particles in a 3D DEM simulation is computationally very expensive. Hence, in order to effectively simulate these laboratory tests in DEM, the specimen size is often scaled down maintaining the grain size distribution same as employed in the experiment. In a parallel approach, the particle size distribution (PSD) is scaled up uniformly keeping the specimen dimensions unaltered. In the present study, the effect of adopting an up-scaled PSD has been explored in reference to the mechanical behavior and instability response of the sand specimen subjected to triaxial compression and extension conditions. In conjunction with the macro-level stress-strain response, the meso-level attributes such as local porosity distribution and particle relative displacement have been also analyzed. The evolution of force chains has been further examined in relation to various adopted PSD scaling. It has been noticed that with increased PSD scaling , higher stresses are attained at macro-level and the stress-strain response exhibits increased oscillations with noticeable fluctuation in the volumetric behavior. Localized instability along with a reduced fluctuation in the stress-strain response can only be perceived when low PSD scaling is adopted.