For many years the empirical prediction of pillar stability has been the dominant method for pillar design. Now, with the advanced numerical modelling of dynamic fracture propagation, it is possible to study the correlation between the empirical pillar load estimates and the actual pillar fracture mechanics. An upgraded version to previously developed constitutive FISH subroutine in FLAC 2D driving the User-Defined-Model which simulates compressive failure behaviour of coal pillars through the development of dynamic fracture propagation. Special insight on peak strength and post failure behaviour is presented through analysis of fracture development as a function of the pillar width to height ratio. Results derived as part of this study show that the numerical fracture propagation in coal pillar produces similar results to the classical empirical estimations of pillar peak loads. The classical progressive shear failure in pillar ribs was observed in the models depicting the probable rib failure mechanisms. Such model is well suited towards providing better understanding of fracture behaviour in rock or coal mass to improve safety when mining within or around complex geological structures.