<p>Grouted rockbolts are the most commonly used ground support systems for reinforcing and stabilizing fractured rock masses, thereby enhancing their load-bearing capacity. Although the deformation mechanics of rockbolts are well-understood under simple loading conditions, such as pull or shear, their behavior becomes less clear under more complex loading scenarios as are often encountered in underground pillar loading within mining scenarios, for example. To address this gap, this study utilized a discrete element modeling approach called bonded block model (BBM) to simulate the behavior of grouted rockbolts installed in large-scale pillar analog specimens that were tested at three different width-to-height (W/H) ratios. As the rock considered contained approximately 26% porosity, two sets of models were developed to represent this porosity implicitly and explicitly. The input properties of the model were refined by calibrating the deformation behavior of the bonded block model to that of previously conducted large-scale laboratory tests. A single set of micro-properties was identified that could produce realistic results for all three W/H ratios. The grouted rockbolt was represented by the built-in rockbolt element in the bonded block model, and the authors found that the use of a tri-linear bond slip model was required in order to match its micro-mechanical axial deformation behavior trend as observed during the laboratory tests. The findings revealed that although the peak strength remained relatively unchanged with the installation of the rockbolt, ductility and residual strength increased, particularly for the W/H = 2 specimen. </p>