Blasting is widely used in rock quarries to produce a substantial amount of fragmented rock however it is challenging to obtain an expected size distribution of muck pile from blast fragmentation due to the presence of discontinuities in rock mass. This study aims to investigate the effect of discontinuity orientation on blast fragmentation of rock. For this purpose, four numerical models of rock benches with single boreholes were constructed using LS DYNA. Discrete element method was utilized to prepare the model combining the bonded particle model (BPM) with the particle blast method (PBM). Joint was introduced manually with variable dip angle (0°, 30°, 59°) and dip-direction(0°, 50°, 102°) to represent the discontinuities. Gradation curve and size distribution parameters such as mean particle size (d50), sieve size at 80% material passing (d80), and uniformity index (n) were obtained from the software. The numerical result was then compared to the field data and found to be satisfactorily aligned. From numerical study, it became evident that the size distribution parameters increase with the decrement of dip angle and dip direction. It was also observed that the change in the dip direction has more influence on the size distribution of muck pile compared to the dip angle. Therefore, the blast operation will produce a coarser muck pile for lower values of dip angle and dip direction. The outcomes of this study are very significant for the field of rock engineering and this framework can be utilized to conduct parametric study to determine optimal blast design parameters to achieve the desired level of rock fragmentation.