Fractured rocks are usually quite complex materials to analyse and simulate numerically. Among several parameters that are difficult to capture in rock modelling, fracture growth always remains a big challenge. Brittle materials such as rocks show a highly non-linear and complex response to external loads, especially in peak and post-peak regions. The overall behaviour of the material is governed by the activation of small including micro fractures and individual grains. The growth of a single fracture when ignored can prove hazardous in large engineering projects. Therefore, utmost importance is to be given to understanding the behaviour of fractures, their initiation, propagation and coalescence. This paper aimed to model rock specimens containing pre-existing flaws, numerically using discrete element formulation. In this study, the modelling of flawed rock specimens is done using discrete element-based software Particle Flow Code in 3-dimension (PFC3D). PFC models rock materials as an assembly of variably sized rigid particles that interact at contact to represent both granular and solid materials. Contact models such as the FLAT jointed model that bonds the complexity of rock and corresponding flaws can be captured. The model is systematically validated with experimental results from the laboratory. The study would help to understand the micromechanics of pre-existing flaws and their corresponding influence on macroscopic behaviour better.